1.判断某一年是不是闰年#include<stdio.h>voidmain(){intyear,month,day,ds;printf("year,month,day=");scanf("%d,%d,%d",&year,&month,&day);ds=day;switch(month-1){case11:ds+=30;case10:ds+=31;case9:ds+=30;case8:ds+=31;case7:ds+=31;case6:ds+=30;case5:ds+=31;case4:ds+=30;case3:ds+=31;case2:if(year%4==0&&year%100!=0||year%400==0)ds+=29;elseds+=28;case1:ds+=31;default:printf("error\n");}printf("itisthedsthdayoftheyear!\n");}2.求最大公约数和最小公倍数#include<stdio.h>voidmain(){inta,b,num1,num2,temp;printf("pleaseinputtwonumber:\n");scanf("%d,%d",&num1,&num2);if(num1<num2){temp=num1;num1=num2;num2=temp;}a=num1;b=num2;while(b!=0){temp=a%b;b=temp;a=b;}printf("gongyueshu:%d\n",a);printf("gongbeishu:%d\n",num1*num2/a);}3.一个7x7的矩阵，求四条边的和。#include<stdio.h>voidmain(){inti,j,a[7][7],sum=0,sum1=0,sum2=0;for(i=0;i<7;i++)for(j=0;j<7;j++)scanf("%d",&a[i][j]);for(i=0;i<7;i++){printf("\n");for(j=0;j<7;j++)printf("%d",a[i][j]);}printf("\n");for(i=0;i<7;i++)for(j=0;j<7;j++)sum1=sum1+a[i][j];printf("%d",sum1);for(i=1;i<6;i++)for(j=1;j<6;j++)sum2=sum2+a[i][j];printf("%d",sum2);sum=sum1-sum2;printf("%d",sum);}4.水仙花数计算#include<stdio.h>voidmain(){inta,b,c,d;scanf("%d",&d);a=d/100;b=d/10%10;c=d%10;if(d==a*a*a+b*b*b+c*c*c)printf("%d是水仙花数",d);elseprintf("这个数不是水仙花数");}5.1判断某一个数是不是素数#include<stdio.h>voidmain(){intn;scanf("%d",&n);inti;for(i=2;i<n-1;i++)if(n%i==0);printf("i不是素数");elseprintf("i是素数");}5.2输出2到20之间的所有素数。#include<stdio.h>voidmain(){inti,k;for(k=2;k<=20;k++){for(i=2;i<k-1;i++)if(k%i==0)break;if(i>=k-1)printf("%4d",k);}}6.输入三个字符，如果其中有小写字母就转换成大写字母输出#include<stdio.h>voidmain(){charch1,ch2,ch3;ch1=getchar();ch2=getchar();ch3=getchar();if(ch1>='a'&&ch1<='z')ch1=ch1-32;if(ch2>='a'&&ch2<='z')ch2=ch2-32;if(ch3>='a'&&ch3<='z')ch3=ch3-32;putchar(ch1);putchar(ch2);putchar(ch3);}