W3

1；；；；

#include <stdio.h>
char score_to_grade(int score);
int main(){int score;char grade;while(scanf("%d",&score)!=EOF){grade=score_to_grade(score);printf("分数：%d,等级：%c\n\n",score,grade);}
return 0;
}
char score_to_grade(int score){char ans;switch (score/10){case 10:case 9:ans='A';break;case 8:ans='B';break;case 7:ans='C';break;case 6:ans='D';break;defult:ans='E';}return ans;}

A1：其是定义了一个函数表明通过分数来转化成等级；形参为int整数型；返回值为char是字符型；

A2：break用于结束循环并结束switch，如果像这样改变ans会直接等于E，会运行在其后面的case中的内容

2：：：：

#include <stdio.h>
int sum_digits(int n);
int main(){int n,ans;while(printf("Enter n:"),scanf("%d",&n)!=EOF){ans=sum_digits(n);printf("n=%d,ans=%d\n\n",n,ans);}return 0;}
int sum_digits(int n){int ans=0;while(n!=0){ans+=n%10;n/=10;}return ans;}

A1；函数的作用是将各个位上的数都加起来

A2：应该可以运行，原代码是用来递归；改后的代码为迭代的方式

3‘’‘

#include<stdio.h>int power(int x,int n);int main(){int x,n;int ans;while(printf("Enter x and n:"),scanf("%d%d",&x,&n)!=EOF){ans=power(x,n);printf("n=%d,ans=%d\n\n",n,ans);}return 0;
}int power(int x,int n){int t=0;if(n==0)return 1;else if(n%2)return x*power(x,n-1);else{t=power(x,n/2);return t*t;}
}

4.。。

#include<stdio.h>
#include<stdlib.h>int is_prime(int i){int ret=1;int k;for(k=2;k<i-1;k++){if(i%k==0){ret=0;break;}}return ret;}int main(){int count=0;printf("100以内的孪生素数：\n");for(int n=2;n<=98;n++){if(is_prime(n)&&is_prime(n+2)){printf("%d %d\n",n,n+2);count++;}}printf("100以内的孪生素数共有%d个\n",count);system("pause");return 0;
}

5/。/。

#include <stdio.h>
int func(int n, int m);int main() {int n, m;int ans;while(scanf("%d%d",&n,&m)!= EOF){int ans = func(n, m);printf("n = %d, m = %d, ans = %d\n\n", n, m, ans);}return 0;
}int func(int n, int m) {if (m < 0 || m > n) return 0;if (m == 0 || m == n) return 1;if (m > n - m) {m = n - m;}int ans = 1;for (int i = 1; i <= m; i++) {ans = ans * (n - m + i) / i;}return ans;
}

6、、、

#include<stdio.h>
int gcd(int a,int b,int c);int main(){int a,b,c;int ans;while(scanf("%d%d%d",&a,&b,&c)!= EOF){ans=gcd(a,b,c);printf("最大公约数：%d\n\n",ans);}return 0;
}int gcd(int a,int b,int c){int min=a;if(b<min) min=b;if(c<min) min=c;for(int i=min;i>=1;i--){if(a%i==0&&b%i==0&&c%i==0){return i;}}return 1;
}

7///

#include <stdio.h>
#include <stdlib.h>
void print_charman(int n);
int main(){int n;printf("Enter n: ");scanf("%d",&n);print_charman(n);return 0;
}void print_charman(int n){int i,j,k;for(i=0;i<n;i++){for(j=0;j<i;j++){printf("\t");}for(k=1;k<2*(n-i);k++){printf(" O\t");}printf("\n");for(j=0;j<i;j++){printf("\t");}for(k=1;k<2*(n-i);k++){printf("<H>\t");}printf("\n");for(j=0;j<i;j++){printf("\t");}for(k=1;k<2*(n-i);k++){printf("I I\t");}printf("\n\n");}
}