刚刚学习了这个程序，思路很简单，就是计算出当年里每个月之前的天数，然后加上当月的天数。唯一注意的应该是不要忘记区分平年和闰年的差别。

1. int main()
   
2. {
   
3. int day, month, year, sum, leap;
   
4. printf("\nplease input year, month, day\n");
   
5. scanf("%d,%d,%d", &year, &month, &day);
   
6. switch(month)/*先计算某月以前月份的总天数*/
   
7. {
   
8. 　case 1: sum = 0; break;
   
9. 　case 2: sum = 31; break;
   
10. 　case 3: sum = 59; break;
    
11. 　case 4: sum = 90; break;
    
12. 　case 5: sum = 120; break;
    
13. 　case 6: sum = 151; break;
    
14. 　case 7: sum = 181; break;
    
15. 　case 8: sum = 212; break;
    
16. 　case 9: sum = 243; break;
    
17. 　case 10: sum = 273; break;
    
18. 　case 11: sum = 304; break;
    
19. 　case 12: sum = 334; break;
    
20. 　default:printf("data error");break;
    
21. }
    
22. sum = sum + day; 　/*再加上某天的天数*/
    
23. 　if((year%4==0 && year%100!=0) || year%400==0)/*判断是不是闰年*/
    
24. 　　leap = 1;
    
25. 　else
    
26. 　　leap = 0;
    
27. if(leap==1 && month>2)/*如果是闰年且月份大于2,总天数应该加一天*/
    
28. sum++;
    
29. printf("It is the %dth day.",sum);

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刚刚学习了这个程序，思路很简单，就是计算出当年里每个月之前的天数，然后加上当月的天数。唯一注意的应该是不要忘记区分平年和闰年的差别。

1. int main()
   
2. {
   
3. int day, month, year, sum, leap;
   
4. printf("\nplease input year, month, day\n");
   
5. scanf("%d,%d,%d", &year, &month, &day);
   
6. switch(month)/*先计算某月以前月份的总天数*/
   
7. {
   
8. 　case 1: sum = 0; break;
   
9. 　case 2: sum = 31; break;
   
10. 　case 3: sum = 59; break;
    
11. 　case 4: sum = 90; break;
    
12. 　case 5: sum = 120; break;
    
13. 　case 6: sum = 151; break;
    
14. 　case 7: sum = 181; break;
    
15. 　case 8: sum = 212; break;
    
16. 　case 9: sum = 243; break;
    
17. 　case 10: sum = 273; break;
    
18. 　case 11: sum = 304; break;
    
19. 　case 12: sum = 334; break;
    
20. 　default:printf("data error");break;
    
21. }
    
22. sum = sum + day; 　/*再加上某天的天数*/
    
23. 　if((year%4==0 && year%100!=0) || year%400==0)/*判断是不是闰年*/
    
24. 　　leap = 1;
    
25. 　else
    
26. 　　leap = 0;
    
27. if(leap==1 && month>2)/*如果是闰年且月份大于2,总天数应该加一天*/
    
28. sum++;
    
29. printf("It is the %dth day.",sum);

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