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PTA 浙大版《C语言程序设计(第4版)》题目集 参考答案(编程题)

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PTA浙大版《C语言程序设计(第4版)》题目集 详解教程

练习2-1 Programming in C is fun! (5 分)

#include<stdio.h>
int main(){
    printf("Programming in C is fun!");
    return 0;
}

练习2-3 输出倒三角图案 (5 分)

#include<stdio.h>
int main(){
    printf("* * * *\n");
    printf(" * * *\n");
    printf("  * *\n");
    printf("   *\n");
    return 0;
}

练习2-4 温度转换 (5 分)

#include<stdio.h>
int main(){
    int C,F=150;
    C=5*(F-32)/9;
    printf("fahr = 150, celsius = %d",C);
    return 0;
}

练习2-6 计算物体自由下落的距离 (5 分)

#include <stdio.h>
int main(){
    float h,t = 3,g = 10;
    h = 0.5*g*t*t;
    printf("height = %.2f",h);
    return 0;
}

练习2-8 计算摄氏温度 (10 分)

#include<stdio.h>
int main(void){
    int C,F;
    scanf("%d",&F);
    C=5*(F-32)/9;
    printf("Celsius = %d",C);
    return 0;
}

练习2-9 整数四则运算 (10 分)

#include<stdio.h>
int main(){
    int m,n;
    scanf("%d %d",&m,&n);
    printf("%d + %d = %d\n",m,n,m+n);
    printf("%d - %d = %d\n",m,n,m-n);
    printf("%d * %d = %d\n",m,n,m*n);
    printf("%d / %d = %d",m,n,m/n);
    return 0;
}

练习2-10 计算分段函数[1] (10 分)

#include<stdio.h>
int main(){
    float x,result;
    scanf("%f",&x);
    if(x!=0){
        result=1/x;
    }else {
        result=0;
    }
    printf("f(%.1f) = %.1f",x,result);
    return 0;
}

练习2-11 计算分段函数[2] (10 分)

#include <stdio.h>
#include <math.h>
int main(){
	float x, y;
	scanf("%f", &x);
	if(x>=0)y=sqrt(x);
	else y=pow(x+1,2)+2*x+1/x;
	printf("f(%.2f) = %.2f", x,y);
	return 0;
}

练习2-12 输出华氏-摄氏温度转换表 (15 分)

for循环版本

#include<stdio.h>
int main(){
    int lower,upper,F;
    float C;
    scanf("%d %d",&lower,&upper);
    F=lower;
    if(lower<=upper&&upper<=100){
        printf("fahr celsius\n");
        C=5.0*(F*1.0-32)/9.0;
        printf("%d%6.1f",F,C);//占据6个字符宽度,靠右对齐,保留1位小数
        for(F=lower+2;F<=upper;F+=2){
            C=5.0*(F*1.0-32)/9.0;
            printf("\n%d%6.1f",F,C);//保证结尾无空行
        }
    }else printf("Invalid.");
    return 0;
}

while循环版本

#include<stdio.h>
int main(){
    int lower,upper,F;
    float C;
    scanf("%d %d",&lower,&upper);
    F=lower;
    if(lower<=upper&&upper<=100){
        printf("fahr celsius\n");
        C=5.0*(F*1.0-32)/9.0;
        printf("%d%6.1f",F,C);//占据6个字符宽度,靠右对齐,保留1位小数
        while((F+=2)<=upper){
            C=5.0*(F*1.0-32)/9.0;
            printf("\n%d%6.1f",F,C);//保证结尾无空行
        }
    }else printf("Invalid.");
    return 0;
}

do-while循环版本

#include<stdio.h>
int main(){
    int lower,upper,F;
    float C;
    scanf("%d %d",&lower,&upper);
    F=lower;
    if(lower<=upper&&upper<=100){
        printf("fahr celsius\n");
        do{
            C=5.0*(F*1.0-32)/9.0;
            printf("%d%6.1f\n",F,C);//占据6个字符宽度,靠右对齐,保留1位小数
        }while((F+=2)<=upper);
    }else printf("Invalid.");
    return 0;
}

练习2-13 求N分之一序列前N项和 (15 分)

#include<stdio.h>
int main(){
    double sum=0;
    int n,i;
    scanf("%d",&n);
    for(i=1;i<=n;i++){
    sum=sum+1.0/i;
    }
    printf("sum = %.6f\n",sum);
    return 0;
}

练习2-14 求奇数分之一序列前N项和 (15 分)

#include<stdio.h>
int main(void){
    double sum=0;
    int n,i;
    scanf("%d",&n);
    for(i=1;i<=n;i++){
    sum=sum+1.0/(2*i-1);
    }
    printf("sum = %.6lf\n",sum);
    return 0;
}

练习2-15 求简单交错序列前N项和 (15 分)

#include<stdio.h>
int main(){
    double sum=0;
    int i,n,flag=1;
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        sum+=1.0/(3*i-2)*(flag);
        flag*=-1;
    }
    printf("sum = %.3lf",sum);
    return 0;
}

练习2-17 生成3的乘方表 (15 分)

#include<stdio.h>
#include<math.h>
int main(){
    int i,n;
    scanf("%d",&n);
    for(i=0;i<=n;i++){
        printf("pow(3,%d) = %.0f\n",i,pow(3,i));
    }
    return 0;
}

练习2-18 求组合数 (15 分)

#include<stdio.h>
double fact(int n){
    double fact=1;
    for(int i=1;i<=n;i++){
        fact*=i;
    }
    return fact;
}
int main(){
    double result;
    double m,n;
    scanf("%lf %lf",&m,&n);
    result = fact(n)/(fact(m)*fact(n-m));
    printf("result = %.0f",result);
    return 0;
}

习题2-1 求整数均值 (10 分)

#include<stdio.h>
int main(){
    int a,b,c,d,sum;
    float average;
    scanf("%d %d %d %d",&a,&b,&c,&d);
    sum=a+b+c+d;
    average=sum/4.0;
    printf("Sum = %d; Average = %.1f",sum,average);
    return 0;
}

习题2-2 阶梯电价 (15 分)

#include<stdio.h>
int main(){
    int n;
    double cost;
    scanf("%d",&n);
    if(n<0){
        printf("Invalid Value!");
        return 0;
    }
    else if(n<=50)cost=0.53*n;
    else cost=50*0.53+0.58*(n-50);
    printf("cost = %.2f",cost);
    return 0;
}

习题2-3 求平方与倒数序列的部分和 (15 分)

#include<stdio.h>
int main(){
    int m,n;
    double sum=0;
    scanf("%d %d",&m,&n);
    for(int i=m;i<=n;i++)
        sum+=i*i+1.0/i;
    printf("sum = %.6f",sum);
    return 0;
}

习题2-4 求交错序列前N项和 (15 分)

#include<stdio.h>
int main(){
    double i,item,sum=0;
    int n,flag=1;
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        item=flag*i/(2*i-1);
        sum+=item;
        flag*=-1;
    }
    printf("%.3f",sum);
    return 0;
}

习题2-5 求平方根序列前N项和 (15 分)

#include<stdio.h>
#include<math.h>
int main(){
    int n,i;
    double sum=0,item;
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        item=sqrt(i);
        sum+=item;
    }
    printf("sum = %.2f",sum);
    return 0;
}

习题2-6 求阶乘序列前N项和 (15 分)

#include<stdio.h>
int main(){
    int n,sum=0,i,j=1;
    scanf("%d",&n);
    for(i=1;i<=n;i++) {
        j*=i;
        sum+=j;
    }
    printf("%d",sum);
}

练习3-2 计算符号函数的值 (10 分)

#include<stdio.h>
int main(){
    int n,sign;
    scanf("%d",&n);
    if(n<0)sign=-1;
    if(n==0)sign=0;
    if(n>0)sign=1;
    printf("sign(%d) = %d",n,sign);
    return 0;
}

练习3-3 统计学生平均成绩与及格人数 (15 分)

#include<stdio.h>
int main(void){
    int i,N,score,count=0;
    double sum=0,average;
    scanf("%d",&N);
    if(N==0){
        printf("average = 0.0\n");
        printf("count = 0");
    }else{
        for(i=1;i<=N;i++){
            scanf("%d",&score);
            sum=sum+score;
            if(score>=60)count++;
        }
        average=sum/N;
        printf("average = %.1f\n",average);
        printf("count = %d",count);
    }
        return 0;
}

练习3-4 统计字符 (15 分)

#include <stdio.h>
int main(){
    int i,letter = 0, blank = 0, digit = 0, other = 0;
    char ch;
    for(i=0;i<=9;i++){
        ch=getchar();
        if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))letter++;
        else if((ch==' ')||(ch=='\n'))blank++;
        else if(ch>='0'&&ch<='9')digit++;
        else other++;
    }
    printf("letter = %d, blank = %d, digit = %d, other = %d",letter,blank,digit,other);
    return 0;
}

练习3-5 输出闰年 (15 分)

#include<stdio.h>
int main(){
    int i,j=0,year;
    scanf("%d",&year);
    if(year<=2000||year>2100)printf("Invalid year!");
    else{
        for(i=2001;i<=year;i++){
            if((i%4==0&&i%100!=0)||(i%400==0)){
            printf("%d\n",i);
            j=1;
            }
        }
        if(j==0)printf("None");
    }
    return 0;
}

练习3-7 成绩转换 (15 分)

#include <stdio.h>
int main(){
    int x;
    scanf("%d",&x);
    switch(x/10){
    case 10:printf("A");break;
    case 9:printf("A"); break;
    case 8:printf("B"); break;
    case 7:printf("C"); break;
    case 6:printf("D"); break;
    default:printf("E");
    }
    return 0;
}

练习3-8 查询水果价格 (15 分)

#include<stdio.h>
int main(void){
    int i,a;
    printf("[1] apple\n[2] pear\n[3] orange\n[4] grape\n[0] exit\n"); 
    for(i=1;i<=5;i++){ 
        scanf("%d",&a);
            if(a==0)break;
            switch(a){
                case 1:printf("price = 3.00\n");break;
                case 2:printf("price = 2.50\n");break;
                case 3:printf("price = 4.10\n");break;
                case 4:printf("price = 10.20\n");break;
                default:printf("price = 0.00\n");
            }
    }
    return 0;
}

习题3-1 比较大小 (10 分)

#include<stdio.h>
int main(){
    int x,y,z,t;
    scanf("%d %d %d",&x,&y,&z);
    if(x>y){t=y;y=x;x=t;}
    if(x>z){t=z;z=x;x=t;}
    if(y>z){t=z;z=y;y=t;}
    printf("%d->%d->%d\n",x,y,z);
    return 0;
}

习题3-2 高速公路超速处罚 (15 分)

#include<stdio.h>
int main(){
    int v,limit;
    double exceed;
    scanf("%d %d",&v,&limit);
    exceed=(v-limit)*100.0/limit;
    if(exceed>=50)printf("Exceed %.f%%. License Revoked",exceed);
    else if(exceed>=10)printf("Exceed %.f%%. Ticket 200",exceed);
    else printf("OK");
    return 0;
}

习题3-3 出租车计价 (15 分)

#include<stdio.h>
int main(){
    double mileage;
    int time,pay;
    scanf("%lf %d",&mileage,&time);
    if(mileage<=3)pay=10;
    else if(mileage<=10)pay=10+2*(mileage-3)+0.5;
    else pay=24+(mileage-10)*3+0.5;
    pay+=time/5*2;
    printf("%d", pay);
    return 0;
}

习题3-4 统计学生成绩 (15 分)

#include<stdio.h>
int main(){
    int n,i,grade,a=0,b=0,c=0,d=0,e=0;
    scanf("%d",&n); 
    for(i=1;i<=n;i++){
        scanf("%d",&grade);
        switch (grade/10){
            case 10: 
            case 9:a++;break;
            case 8:b++;break;
            case 7:c++;break;
            case 6:d++;break;
            default:e++;break;
        }
    }
    printf("%d %d %d %d %d",a,b,c,d,e);
    return 0;
}

习题3-5 三角形判断 (15 分)

#include<stdio.h>
#include<math.h>
int main(){
    double x1,y1,x2,y2,x3,y3,p,s;
    double j,k,l;
    scanf("%lf %lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&x3,&y3);
    j=sqrt(pow(x1-x2,2)+pow(y1-y2,2));
    k=sqrt(pow(x2-x3,2)+pow(y2-y3,2));
    l=sqrt(pow(x1-x3,2)+pow(y1-y3,2));
    if(j+k>l&&k+l>j&&j+l>k){
        p=(j+k+l)/2;
        s=sqrt(p*(p-j)*(p-k)*(p-l));//海伦公式
        printf("L = %.2lf, A = %.2lf",p*2,s);
    }
    else printf("Impossible");
    return 0;
}

练习4-3 求给定精度的简单交错序列部分和 (15 分)

#include<stdio.h>
int main (){
    double sum=0,eps,item;
    int n=1,flag=1;
    scanf("%lf",&eps);
    do{
        item=1.0/(3*n-2);
        sum+=flag*item;
        flag=-flag;
        n++;
    }while(item>eps);
    printf("sum = %f",sum);
    return 0;
}

练习4-6 猜数字游戏 (15 分)

while循环

#include <stdio.h>
int main(){
	int random,i=1,n,input;
	scanf("%d %d",&random,&n);
    scanf("%d",&input);
    while(i<=n&&input>=0){
		if(i==1&&input==random){
			printf("Bingo!\n");
			break;
		}
		if((i==2||i==3)&&input==random){
			printf("Lucky You!\n");
			break;
		}
		if(i>3&&input==random){
			printf("Good Guess!\n");
			break;
		}
		if(input>random)
			printf("Too big\n");
		if(input<random)
			printf("Too small\n");
        scanf("%d",&input);
		i++;
	}
	if (i==n+1||input<0)
		printf("Game Over");
	return 0;
}

for循环

#include<stdio.h>
int main (){
    int random,n,i,a;
    scanf("%d %d",&random,&n);
    for(i=1;i<=n;i++){
        scanf("%d",&a);
        if(a<0){printf("Game Over\n");break;}
        if(a==random){
            if(i==1){printf("Bingo!");break;}
            else if(i<=3){printf("Lucky You!");break;}
            else if(i<=n){printf("Good Guess!");break;}
        }
        if(a>random)printf("Too big\n");
        if(a<random)printf("Too small\n");
        if(i==n)printf("Game Over\n");
    }
    return 0;
}

练习4-7 求e的近似值 (15 分)

#include<stdio.h>
int main(){
    double e=1,fact=1;
    int n;
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        fact*=i;
        e+=1/fact;
    }
    printf("%.8lf",e);
    return 0;
}

练习4-10 找出最小值 (20 分)

#include<stdio.h>
int main(){
    int min,n,temp;
    scanf("%d",&n);
    scanf("%d",&min);
    for(int i=1;i<n;i++){
        scanf("%d",&temp);
        if(temp<min)min=temp;
    }
    printf("min = %d",min);
    return 0;
}

练习4-11 统计素数并求和 (20 分)

#include<stdio.h>
int main(){
    int M,N,count=0,sum=0,i,j;
    scanf("%d %d",&M,&N);
    for(i=M;i<=N;i++){
        for(j=2;j<i;j++)
            if(i%j==0)break;
        if(i==j){
            count++;
            sum+=i;
        }
    }
    printf("%d %d",count,sum);
    return 0;
}

习题4-1 求奇数和 (15 分)

#include<stdio.h>
int main(){
    int num,sum=0;
    do{
        scanf("%d",&num);
        if(num>0&&num%2==1)sum+=num;
    }while(num>0);
    printf("%d",sum);
    return 0;
}

习题4-2 求幂级数展开的部分和 (20 分)

#include <stdio.h>
#define eps 0.00001
int main(){
    double x,sum=1,item = 1.0,n = 1.0;
    scanf("%lf",&x);
    while(item>=eps){
        item *= x/n;
        sum+=item;
        n++;
    }
    printf("%.4f",sum);
    return 0;
}

习题4-3 求分数序列前N项和 (15 分)

#include <stdio.h>
int main(){
	int n,i;
	double a=2,b=1,temp,sum=0;
	scanf("%d", &n);
	for(i=1;i<=n;i++){
		sum+=a/b;
        temp=a;
        a+=b;
        b=temp;
	}
	printf("%.2f",sum);
	return 0;
}

习题4-4 特殊a串数列求和 (20 分)

#include<stdio.h>
int main(){
    int a,n,i,item=0,sum=0;
    scanf("%d %d",&a,&n);
    for(i=1;i<=n;i++){
        item=item*10+a;
        sum+=item;
    }
    printf("s = %d",sum);
    return 0;
}

习题4-5 换硬币 (20 分)

# include <stdio.h>
int main(){
    int count=0,i,j,k;
    double x;
    if(scanf("%lf",&x)==1);
    for(i=x/5;i>=1;i--){
        for(j=(x-5*i)/2;j>=1;j--){
            for(k=x-5*i-2*j;k>=1;k--){
                if(5*i+2*j+k==x){
                    printf("fen5:%d, fen2:%d, fen1:%d, total:%d\n",i,j,k,i+j+k);
                    count++;
                }
            }
        }
    }
    printf("count = %d",count);
    return 0;
}

习题4-6 水仙花数 (20 分)

#include <stdio.h>
int ipow( int x, int n);
int main() {
	int N, i,j,temp,remainder,Npower, sum;
	scanf("%d", &N);
	for (i = ipow(10, N - 1); i < ipow(10, N ); i++) {
		sum = 0;
		temp = i;
		while (temp != 0) {
            Npower=1;
            remainder=temp % 10;
            Npower=ipow(remainder,N);
			sum += Npower;
			temp /= 10;
		}
		if (i == sum)printf("%d\n", i);
	}
	return 0;
}
int ipow( int x, int n){
    int i, p=1;
    for (i=0; i<n; i++) p *=x;
    return p;
}

习题4-7 最大公约数和最小公倍数 (15 分)

#include <stdio.h>
int GCD( int M, int N);
int main(){
    int M, N, gcd, lcm;
    scanf("%d %d", &M, &N);
    if (M>N) gcd = GCD(M, N);
    else gcd = GCD(N, M);
    lcm=M*N/gcd;
    printf("%d %d\n", gcd, lcm);
    return 0;
}
int GCD( int M, int N){
    int r = M%N;
    while (r) {
          M = N; N = r;
          r = M%N;
    }
    return N; 
}

习题4-8 高空坠球 (20 分)

#include<stdio.h>
int main(){
    int i,n;
    double H,h,s;
    scanf("%lf %d",&H,&n);
    if(n==0)printf("0.0 0.0");
    else {
        s=H;
        h=H/2;
        for(i=2;i<=n;i++){
            s+=2*h;
            h/=2;
        }
        printf("%.1lf %.1lf",s,h);
    }
    return 0;
}

习题4-9 打印菱形图案 (15 分)

#include<stdio.h>
int main(){
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n/2+1;i++){
		for(int j=(n/2+1-i)*2;j>=1;j--)printf(" ");
		for(int j=1;j<=2*i-1;j++)printf("* ");
		printf("\n");
	}
	for(int i=1;i<=n/2;i++){
		for(int j=1;j<=2*i;j++)printf(" ");
		for(int j=n-2*i;j>=1;j--)printf("* ");
		printf("\n");
	}
	return 0;
}

习题4-10 猴子吃桃问题 (15 分)

#include<stdio.h>
int main(){
	int n,i,sum=0,num=1;
	scanf("%d",&n);
	for(i=n-1;i>=1;i--){
	  sum=(num+1)*2;
	  num=sum;
	}
	printf("%d",sum);
	return 0;
}

习题4-11 兔子繁衍问题 (15 分)

//斐波那契数列
#include<stdio.h>
int main(){
    int month,N,F1=1,F2=1,F3=0;
    //F1,F2,F3表示连续三个月的兔子数量
    scanf("%d",&N);
    if(N==1)month=1;
    else{
        month=2;
        while(F3<N){
            F3=F1+F2;
            F1=F2;
            F2=F3;
            month++;
        }
    }
    printf("%d",month);
    return 0;
}

练习6-3 英文字母替换加密(大小写转换+后移1位) (15 分)

#include<stdio.h>
int main(){
    char c,delta;
    delta='A'-'a';
    do{
        scanf("%c",&c);
        if(c>='a'&&c<'z')c+=(delta+1);
        else if(c>='A'&&c<'Z')c-=(delta-1);
        else if(c=='Z')c='a';
        else if(c=='z')c='A';
        printf("%c",c);
    }while(c!='\n');
    return 0;
}

习题6-7 简单计算器 (20 分)

#include<stdio.h>
int main(){
    int a,sum;
    char c;
    scanf("%d",&sum);
    while((c=getchar())!='='){
        scanf("%d",&a);
        switch(c){
            case '+':sum+=a;break;
            case '-':sum-=a;break;
            case '*':sum*=a;break;
            case '/':
                if(a==0){
                    printf("ERROR");
                    return 0;
                }
                else sum/=a;
                break;
            default:printf("ERROR");
                    return 0;
        }
    }
    printf("%d",sum);
    return 0;
}

习题6-8 单词首字母大写 (15 分)

#include<stdio.h>
int main(){
	char ch,prev=' ';
	while((ch=getchar())!='\n'){
		if (ch>='a'&&ch<='z'&&prev==' ') ch=ch-'a'+'A';
		putchar(ch);
		prev=ch;
	}
	return 0;
}

练习7-2 求最大值及其下标 (20 分)

#include<stdio.h>
int main(){
    int n,i,max,index=0;
    scanf("%d",&n);
    int a[n];
    for(i=0;i<n;i++)scanf("%d",&a[i]);
    max=a[0];
    for(i=0;i<n;i++){
        if(a[i]>max){
            max=a[i];
            index=i;
        }
    }
    printf("%d %d",max,index);
    return 0;
}

练习7-3 将数组中的数逆序存放 (20 分)

#include<stdio.h>
int main(){
    int n,i;
    scanf("%d",&n);
    int a[n];
    for(i=n-1;i>=0;i--)scanf("%d",&a[i]);
    for(i=0;i<n-1;i++)printf("%d ",a[i]);
    printf("%d",a[n-1]);
    return 0;
} 

练习7-4 找出不是两个数组共有的元素 (20 分)

#include <stdio.h>
int main() {
    int n, m, i, j, flag,cnt=0;
    scanf("%d", &n);
    int a[n];
    for (i = 0; i < n; i++)scanf("%d", &a[i]);
    scanf("%d", &m);
    int b[m];
    int s[m+n];
    for (j = 0; j < m; j++)scanf("%d", &b[j]);
    for (i = 0; i < n; i++) {
        flag = 0;
        for (j = 0; j < m; j++) {
            if (a[i] == b[j]) {
                flag = 1;
                break;
            }
        }
        if (flag == 0) {
                s[cnt]=a[i];
                cnt++;
        }
    }
    for (j = 0; j < m; j++) {
        flag = 0;
        for (i = 0; i < n; i++) {
            if (a[i] == b[j]) {
                flag = 1;
                break;
            }
        }
        if (flag == 0) {
            s[cnt]=b[j];
            cnt++;
        }
    }
    printf("%d",s[0]);
    for(i=1;i<cnt;i++){
        flag=0;
        for(j=0;j<i;j++){
            if(s[i]==s[j]){
                flag=1;
                break;
            }
        }
        if(flag==0)printf(" %d",s[i]);
    }
    return 0;
}

练习7-7 矩阵运算 (20 分)

#include<stdio.h>
int main(){
    int i,n,j,s=0;
    scanf("%d",&n);
    int a[n][n];
    for(i=0;i<n;i++)for(j=0;j<n;j++)scanf("%d",&a[i][j]);
    for(i=0;i<n;i++)for(j=0;j<n;j++)if(j!=n-1-i&&i!=n-1&&j!=n-1)s+=a[i][j];
    printf("%d",s);
    return 0;
}

练习7-8 方阵循环右移 (20 分)

#include<stdio.h>
int main(){
    int m,n,i,j;
    scanf("%d %d",&m,&n);
    int a[m][n],b[m][n];
    m=m%n;
    for(i=0;i<=n-1;i++)for(j=0;j<=n-1;j++)scanf("%d ",&a[i][j]);
    for(i=0;i<=n-1;i++){
        for(j=0;j<=n-1;j++){
            if(j+m>(n-1))b[i][j+m-n]=a[i][j];
            else b[i][j+m]=a[i][j];
        }
    }
    for(i=0;i<=n-1;i++){
        for(j=0;j<=n-1;j++)printf("%d ",b[i][j]);
        printf("\n");
    }
    return 0;
}

练习7-9 计算天数 (15 分)

#include <stdio.h>
int main(){
    int i,year,month,day,n=0,
    a[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
    scanf("%d/%d/%d",&year,&month,&day);
    if((year%4==0&&year%100)||year%400==0)a[2]=29;
    for(i=1;i<month;i++)n+=a[i];
    printf("%d",n+day);
    return 0;
}

练习7-10 查找指定字符 (15 分)

#include<stdio.h>
int main(){
    char ch,c[80];
    int i=0,j,flag=0,index;
    ch=getchar();
    getchar();
    while((c[i]=getchar())!='\n')i++;
    for(j=0;j<i;j++)
        if(ch==c[j]){
            index=j;
            flag=1;
        }
    if(flag==1)printf("index = %d",index);
    else printf("Not Found");
    return 0;
}

练习7-11 字符串逆序 (15 分)

#include <stdio.h>
int main(){
    int n=0,i;
    char a[80];
    while((a[n]=getchar())!='\n')n++;
    for(i=n-1;i>=0;i--)printf("%c",a[i]);
    return 0;
}

习题7-1 选择法排序 (20 分)

#include<stdio.h>
int main(){
    int i,j,n,temp;
    scanf("%d",&n);
    int a[n];
    for(i=0;i<n;i++)scanf("%d",&a[i]);
    for(i=0;i<n;i++){
        temp = a[i];
        for(j=i;j<n;j++)
            if(a[j]>a[i]){
                a[i] = a[j];
                a[j] = temp;
                temp = a[i];
            }
    }
    printf("%d",a[0]);
    for(int i=1;i<n;i++)printf(" %d",a[i]);
}

习题7-2 求一批整数中出现最多的个位数字 (20 分)

#include<stdio.h>
int main(){
    int n,cnt_max,i;
    scanf("%d",&n);
    int a[n],b[10]={0};
    for(i=0;i<n;i++)scanf("%d",&a[i]);
    for(i=0;i<n;i++){
        do{
            b[a[i]%10]++;
            a[i]/=10;
        }while(a[i]!=0);
    }
    cnt_max=b[0];
    for(i=1;i<10;i++)if(cnt_max<b[i])cnt_max=b[i];
    printf("%d:",cnt_max);
    for(i=0;i<10;i++)if(b[i]==cnt_max)printf(" %d",i);
    return 0;
}

习题7-3 判断上三角矩阵 (15 分)

#include <stdio.h>
int main(){
    int T,i,j,k,l,flag;
    scanf("%d",&T);
    int a[T];
    int b[T][11][11];
    for(i=0;i<T;i++){
        scanf("%d",&a[i]);
        j = a[i];
        for(k=0;k<j;k++)
            for(l=0;l<j;l++)
                scanf("%d",&b[i][k][l]);
    }
    for(i=0;i<T;i++){
        j = a[i];
        flag = 1;
        for(k=1;k<j;k++){
            for(l=0;l<k;l++){
                if(b[i][k][l]){
                    flag=0;
                    break;
                }
            }
            if(!flag)break;
        }
        if(flag)printf("YES\n");
         else{
            printf("NO\n");
            flag = 0;
        }
    }
    return 0;
}

习题7-4 求矩阵各行元素之和 (15 分)

#include<stdio.h>
int main(){
    int m,n,sum=0;
    scanf("%d %d",&m,&n);
    int a[m][n],i,j;
    for(i=0;i<m;i++)
        for(j=0;j<n;j++)
            scanf("%d",&a[i][j]);
    for(i=0;i<m;i++){
        for(j=0;j<n;j++)
            sum+=a[i][j];
        printf("%d\n",sum);
        sum=0;
    }
    return 0;
}

习题7-5 找鞍点 (20 分)

#include<stdio.h>
int main(){
    int n,i,j,k;
    int max,flag;
    scanf("%d",&n);
    int a[n][n];
    for(i=0;i<n;i++)for(j=0;j<n;j++)scanf("%d",&a[i][j]);
    for(i=0;i<n;i++){
        max=0;
        for(j=0;j<n;j++)if(a[i][j]>=a[i][max])max=j;
        flag=1;
        for(k=0;k<n;k++)if(a[i][max]>a[k][max])flag=0;
        if(flag){
            printf("%d %d\n",i,max);
            break;
        }
    }
    if(flag==0)printf("NONE");
    return 0;
}

习题7-6 统计大写辅音字母 (15 分)

参考答案1

if分支

#include<stdio.h>
int check ( char c ){
    if( c<'A' || c>'Z' ) return 0;
    if(c!='A'&&c!='E'&&c!='I'&&c!='O'&&c!='U')
        return 1;
    else return 0;
}
int main(){
    char a[80];
    int cnt=0,i=0;
    while((a[i]=getchar())!='\n')i++;
    for(i=0;a[i]!='\n';i++)
        cnt+=check (a[i]);
    printf("%d",cnt);
    return 0;
}

参考答案2

switch-case分支

#include <stdio.h>
int check ( char c ){
    int ret;
    if ( c<'A' || c>'Z' ) return 0;
    switch (c) {
    case 'A': 
    case 'E': 
    case 'I': 
    case 'O': 
    case 'U': 
        ret=0; break;
    default: ret=1; break;
    }
    return ret;
}
int main(){
    char c;
    int cnt = 0;
    while ( (c=getchar())!='\n' ) 
        cnt += check(c);
    printf("%d\n", cnt);
    return 0;
}

习题7-7 字符串替换 (15 分)

参考答案1

#include <ctype.h>

#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main(){
    char str[81];
    gets(str);
    for( int i=0; i<strlen(str); i++ )
        if( isupper(str[i]) )str[i]='A'+'Z'-str[i];
    for( int i=0; i<strlen(str); i++ )printf("%c",str[i]);
    return 0;
}

参考答案2

自定义函数

#include <stdio.h>
#include <string.h>
int isupper(char c){
    int isupper=0;
    if(c>='A'&&c<='Z')isupper=1;
    return isupper;
}
int main(){
    char str[81];
    gets(str);
    for( int i=0; i<strlen(str); i++ )
        if( isupper(str[i]) )str[i]='A'+'Z'-str[i];
    for( int i=0; i<strlen(str); i++ )printf("%c",str[i]);
    return 0;
}

习题7-8 字符串转换成十进制整数 (15 分)

#include<stdio.h>
int main(){
    int i=0,j,flag=0,n=0;
    char ch,a[80];
    a[0]='\0';
    while((ch=getchar())!='#'){
        if(ch=='-'&&a[0]=='\0'){
            a[i]=ch;
            i++;
        }
        if((ch>='a'&&ch<='f')||(ch>='A'&&ch<='F')||(ch>='0'&&ch<='9')){
            a[i]=ch;
            i++;
            flag=1;
        }
    }
    if(a[0]=='-'&&flag)printf("-");
    j=i;
    for(i=0;i<j;i++){
        if(a[i]>='0'&&a[i]<='9')n=n*16+a[i]-'0';
        else if(a[i]>='A'&&a[i]<='Z')n=n*16+a[i]-'A'+10;
        else if(a[i]>='a'&&a[i]<='z')n=n*16+a[i]-'a'+10;
    }
    printf("%d",n);
    return 0;
}

习题8-7 字符串排序 (20 分)

#include<stdio.h>
#include<string.h>
#define N 5
#define M 80
int main(){
    char str[N][M]={'0'};
    int i,j;
    for(i=0;i<N;i++)scanf("%s",str[i]);
    char temp[M];
    for(i=0;i<N;i++){
        for(j=i+1;j<N;j++){
            if(strcmp(str[i],str[j]) >= 0){
                strcpy(temp, str[i]);
                strcpy(str[i], str[j]);
                strcpy(str[j], temp);
            }
        }
    }
    printf("After sorted:\n");
    for(int i=0;i<N;i++)printf("%s\n",str[i]);
    return 0;
}

习题8-10 输出学生成绩 (20 分)

本题题干建议使用动态内存分配

#include<stdio.h>
#include<stdlib.h>
int main(){
    int n,i;
    scanf("%d",&n);
    float *score,sum,average,min,max;
    score=(float*)malloc(sizeof(n*score[0]));
    scanf("%f",&score[0]);
    min=score[0];
    max=score[0];
    sum=score[0];
    for(i=1;i<n;i++){
        scanf("%f",&score[i]);
        if(score[i]>max)max=score[i];
        if(score[i]<min)min=score[i];
        sum+=score[i];
    }
    average=sum/n;
    printf("average = %.2f\n",average);
    printf("max = %.2f\n",max);
    printf("min = %.2f",min);
    free(score);
    return 0;
}

习题9-1 时间换算 (15 分)

#include <stdio.h>
struct time {
    int h, m, s;
} T;
int main(){
    int n;
    scanf("%d:%d:%d\n", &T.h, &T.m, &T.s);
    scanf("%d", &n);
    T.s += n;
    if (T.s >= 60) {
        T.s -= 60;
        T.m++;
        if (T.m >=60) {
            T.m -= 60;
            T.h++;
            if (T.h==24) T.h = 0;
        }
    }
    printf("%02d:%02d:%02d\n", T.h, T.m, T.s);
    return 0;
}

习题9-3 平面向量加法 (15 分)

#include <stdio.h>
struct Vec {
    double x, y;
};
int main(){
    struct Vec v1, v2;
    double x,y;
    scanf("%lf %lf %lf %lf", &v1.x, &v1.y, &v2.x, &v2.y);
    x = v1.x + v2.x;
    y = v1.y + v2.y;
    if ((x>-0.05) && (x<0)) x = 0.0;
    if ((y>-0.05) && (y<0)) y = 0.0;
    printf("(%.1f, %.1f)", x, y);
    return 0;
}

习题9-4 查找书籍 (20 分)

参考答案1

#include <stdio.h>
#include <string.h>
struct Book{
    double price;
    char name[31];
};
int main(){
    int n;
    scanf("%d",&n);
    struct Book book[n];
    int i,max = 0,min = 0;
    for(i=0; i<n; i++){
        getchar();
        gets(book[i].name);
        scanf("%lf",&book[i].price);
        if(book[i].price>book[max].price)max = i;
        if(book[i].price<book[min].price)min = i;
    }
    printf("%.2lf, %s\n",book[max].price,book[max].name);
    printf("%.2lf, %s\n",book[min].price,book[min].name);
    return 0;
}

参考答案2

学习使用enum

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef enum{false, true} bool;
struct book_info {
    double price;
    char name[31];
};
int main(){
    int n;
    struct book_info highest, lowest, cur;
    bool first = true;
    scanf("%d\n", &n);
    while(n--) {
        gets(cur.name);
        scanf("%lf\n", &cur.price);
        if(first) {
            highest.price = cur.price;
            strcpy(highest.name, cur.name);
            lowest.price = cur.price;
            strcpy(lowest.name, cur.name);
            first = false;
            continue;
        }
        if(cur.price > highest.price) {
            highest.price = cur.price;
            strcpy(highest.name, cur.name);
        } else if(cur.price < lowest.price) {
            lowest.price = cur.price;
            strcpy(lowest.name, cur.name);
        }
    }
    printf("%.2f, %s\n", highest.price, highest.name);
    printf("%.2f, %s\n", lowest.price, lowest.name);
    return 0;
}

习题9-5 通讯录排序 (20 分)

参考答案1

自定义选择排序

#include <stdio.h>
#include <stdlib.h>
struct friends {
	char name[11];
	int birth;
	char tele[18];
} friend[11];

void sort(struct friends friend[],int n){
	struct friends temp;
	for(int i=0;i<n;i++){
		for(int j=i+1;j<n;j++){
			if(friend[i].birth>friend[j].birth){
				temp=friend[i];
				friend[i]=friend[j];
				friend[j]=temp;
			}
		}
	}
}

int main() {
	int n, i;
	scanf("%d", &n);
	for (i = 0; i < n; i++) {
		getchar();
		scanf("%s%d%s", friend[i].name, &friend[i].birth, friend[i].tele);
	}
	sort(friend, n);
	for (i = 0; i < n; i++) printf("%s %d %s\n", friend[i].name, friend[i].birth, friend[i].tele);
	return 0;
}

参考答案2

qsort排序

#include <stdio.h>
#include <stdlib.h>
struct friends {
    char name[11];
    int birth;
    char tele[18];
} friend[9];

int cmp(const void *a, const void *b) {
    return ((struct friends *)a)->birth > ((struct friends *)b)->birth;
}

int main() {
    int n, i;
    scanf("%d", &n);
    for (i = 0; i < n; i++) {
        getchar();
        scanf("%s%d%s", friend[i].name, &friend[i].birth, friend[i].tele);
    }
    qsort(friend, n, sizeof(struct friends), cmp);
    for (i = 0; i < n; i++) printf("%s %d %s\n", friend[i].name, friend[i].birth, friend[i].tele);
    return 0;
}
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