如何对抗强拆:程序问题

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输入年和天数,输出对应的月和日.
分析:1、应先分出闰年与非闰年;
2、如果总天数大于当月天数，总天数减去当月天数，再与下一月天数比较；
3、当总天数小于当月天数时，输出当月及当月天数；
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#include <stdio.h>
int month_day(int year,int yearday,int *pmonth,int *pday);

void main()
{
int day,month,year,yearday;
printf("input year and yearday!\n");
scanf("%d%d",&year,&yearday);
month_day(year,yearday,&month,&day);
printf("%d-%d-%d\n",year,month,day);
}
int month_day(int year,int yearday,int *pmonth,int *pday)
{
int leap,k;
int tab[2][13]={{0,31,28,31,30,31,30,31,31,30,31,30,31},
{0,31,29,31,30,31,30,31,31,30,31,30,31}};
leap=(year%4==0&&year%100!=0)||year%400==0;
for(*pmonth=1;yearday>tab[leap][*pmonth];*pmonth++)//1
yearday=yearday-tab[leap][*pmonth];//2
*pday=yearday;
//*pmonth=k; //3
return *pday;
}

以上程序,为什么我运行时，输入2006 300时会出现错误，而我把1、2处的*pmonth用t代替后，把3处定义好，程序可以正常，我怎么想都想不明白，请高手指点！！