#include<stdio.h>

int ping_month[]={31,28,31,30,31,30,31,31,30,31,30,31};

int run_month[]={31,29,31,30,31,30,31,31,30,31,30,31};

int main(void){

int week,day,i=1,j,space,end;

int year,month;

printf("please input the year and month that you want to show:\n");

scanf("%d%d",&year,&month);

if(is_run(year))

day=run_month[month-1];

else

day=ping_month[month-1];

week=week_day(year,month);

//控制输出格式

printf("\n\n\t\t=========%d年%d月=========\t\t\n",year,month);

printf("\tSUN\tMON\tTUE\tWED\tTHU\tFRI\tSAT\n");

while(i<=day){

space=week%7;

end = 6-space+i;

for(j=1;j<=7;++j){

if (j<=space) {

printf("\t ");

week=7;

}

else if(i<=end&&i<=day){

printf("\t%d ", i);

++i;

}

}

putchar('\n');

}

return 0;

}

//返回指定年月的的1号是周几

//已知1970年1月1日为周四，6月1日为周一

int week_day(int year, int month){

int week_map[] = {3,4,5,6,7,1,2};

int days = 1;

int i,w;

for (i=1970; i<year; i++) {//求年的天数

if(is_run(i))

days+=366;

else

days+=365;

}

days+=count_day(year,1,month);

return week_map[days%7];

}

//判断是否是闰年

int is_run(int year){

if((year%4==0&&year%100!=0)||(year%400==0))

return 1;

return 0;

}

//计算某年内from月到to月的天数

count_day(int year,int from , int to){

int i,d=0;

for(i=from;i<to;++i){

d+=ping_month[i-1];

}

if(is_run(year))

d+=1;

return d;

}