c语言打印日历

#include<stdio.h>
int main(void)
{
    int i,y,m,days,lp ,leap;
    printf("请输入年/月：");
    scanf("%d/%d",&y,&m);
    leap=(y%4==0&&y%100!=0||y%400==0);

    for(i=1;i<m;i++){
        switch(i){
            case 1:  case 3: case 5: case 7: case 8: case 10:case 12:
                days+=31;break;
            case 4: case 6: case 9: case 11:
                days+=30;break;
            case 2: days +=28+ leap;break;
            default: break;
        }
    }
    days += 1;//求y年m月1号是y年的第days天
    int ye, week=1 ;
    for(ye=1990;ye<y;ye++){
        lp=(ye%4==0&&ye%100!=0||ye%400==0);
        days+=365+lp;
    }        //求输入的月份1号是从1990起第days天。
    
    int wd,day; //当天周几；
    wd= days%7;
    printf("%d\n",wd);//调试
    printf("   %d 月 %d   \n",m,y);
    printf("日 一 二 三 四 五 六\n");
    
    
    switch(m){
        case 1:  case 3: case 5: case 7: case 8: case 10:case 12:
            day=31;break;
        case 4: case 6: case 9: case 11:            
            day=30;break;
        case 2: day =28+ leap;break;
        default: break;
        
    }
    
    for(i=0;i<wd;i++) printf("   ");
    for(i = 1;i<=day;i++){
        printf("%2d ",i);
        if((i+wd)%7==0) printf("\n");
    }
    printf("\n");
    return 0;


}