C语言用switch语句实现输入某年某月某日，判断这一天是这一年的第几天

以下是使用C语言的switch语句实现输入某年某月某日，判断这一天是这一年的第几天的代码：

#include <stdio.h>

int main()
{
    int year, month, day, sum = 0;
    printf("请输入年月日，格式为：年 月 日\n");
    scanf("%d %d %d", &year, &month, &day);
    switch (month) {
        case 1: sum = 0; break;
        case 2: sum = 31; break;
        case 3: sum = 59; break;
        case 4: sum = 90; break;
        case 5: sum = 120; break;
        case 6: sum = 151; break;
        case 7: sum = 181; break;
        case 8: sum = 212; break;
        case 9: sum = 243; break;
        case 10: sum = 273; break;
        case 11: sum = 304; break;
        case 12: sum = 334; break;
        default: printf("输入的月份有误！\n"); return 0;
    }
    sum += day;
    if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
        if (month > 2) {
            sum++;
        }
    }
    printf("%d年%d月%d日是该年的第%d天。\n", year, month, day, sum);
    return 0;
}