法一：#include <stdio.h>int main(){    int i,sum = 0;    i = 1;    while(i<=100){        sum += i;        i++;    }    printf("sum = %d\n",sum);    return 0;}法二：#include <stdio.h>int main(){    int i,sum = 0;    i = 1;    sum = 0;    do{        sum += i;        i++;    }while(i<=100);    printf("sum = %d\n",sum);    return 0;}法三：#include <stdio.h>int main(){    int i,sum = 0;    sum = 0;    for(i=1;i<=100;i++)        sum += i;    printf("sum = %d\n",sum);    return 0;}

法一：#include <stdio.h>int main(){    int n,i,jiec=1;    printf("请输入一个整数n：");    //n:从键盘输入    scanf("%d",&n);    i = n;    while(i>=1){        jiec = jiec * 1;        i--;    }     printf("%d!=%d\n",n,jiec);return 0;}法二：#include <stdio.h>int main(){        //while循环求n!=1*2*... ...*(n-1)*n    int n,i,jiec=1;    printf("请输入一个整数n：");     //n:从键盘输入    scanf("%d",&n);     i = 1; jiec = 1;    while(i<=n){        jiec = jiec * i;        i++;    }     printf("%d!=%d\n",n,jiec);    return 0;}    

#include <stdio.h>int main(){    //使用for循环完成1+2+... ...+100    int k,sum = 0;    for(k=1;k<=100;k++)        sum += k;    printf("sum=%d\n",sum);        for(k=1;k<=50;k++)        sum = sum + k*k;    printf("sum=%d\n",sum);        for(k=1;k<=10;k++)        sum = sum + 1/k;    printf("sum=%d\n",sum);    return 0;}

#include <stdio.h>int main(){    char c;    int zm=0,sz=0,kg=0,qt=0;    while((c=getchar())!=‘\n‘){        if((c>=‘a‘ && c<=‘z‘)||(c>=‘A‘ && c<=‘Z‘))             zm++;        else if(c>=‘0‘ && c<=‘9‘)             sz++;        else if(c==‘ ‘)             kg++;        else             qt++;    }        printf("字母个数：%d\n",zm);        printf("数字个数：%d\n",sz);        printf("空格个数：%d\n",kg);        printf("其他个数：%d\n",qt);        return 0; }

#include <stdio.h>int main(){    //m,n的最大公约数 能够同时整除m和n的最大数     int m,n,t,i,gys=1,gbs;    printf("请输入两个整数：");    scanf("%d%d",&m,&n);    //m的位置放大的数    if(n>m){        t=m;        m=n;        n=t;    }     for(i=n;i>=1;i--)        if(m%i==0&&n%i==0)            break;        printf("m=%d,n=%d",m,n);    if(i!=0){         gys=i;         printf("最大公约数为：%d\n",gys);        }        gbs=m*n/gys;          printf("最大公倍数为：%d\n",gbs);                  return 0;}

#include <stdio.h>int main(){    //水仙花束    int n,k1,k2,k3;  //k1个位，k2十位，k3百位    for(n=100;n<=999;n++){        k1=n % 10;        k2=n / 10 %10;        k3=n / 100;        if(n==k1*k1*k1+k2*k2*k2+k3*k3*k3)            printf("%d\n",n);    }     return 0;}