输入年月日，判别这一天是这一年的第几天

#include<stdio.h>
#include<conio.h>
int main() {
    
    
	int day,month,year,sum,leap;
	printf("please input year,month,day");
	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("出错了");
			break;
	}
	sum=sum+day;
	if(year%400==0||(year%4==0&&year%100!=0))
		leap=1;
	else
		leap=0;
	if(leap==1&&month>2)
		sum++;
	printf("It is the %dth day",sum);
	getch();
}

Python

#!/usr/bin/python
from datetime import *
d=input()
d1=datetime.strptime(d[:4]+'/1/1','%Y/%m/%d')
d2=datetime.strptime(d,'%Y/%m/%d')
print((d2-d1).days+1)

Java

package com.lx;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * 题目：输入某年某月某日，判断这一天是这一年的第几天？
 */
public class Demo {
    
    
		public static void main(String[] args) {
    
    
			BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
			try {
    
    
				//录入键盘的数据
				String str=bf.readLine();
				//分割年月日
				String[] strArr=str.split("-");
				int year=Integer.parseInt(strArr[0]);
				int month=Integer.parseInt(strArr[1]);
				int towMonth=28;
				//判断平年还是闰年
				if((year%4==0&&year%100!=0)||(year%400==0)) {
    
    
					towMonth=29;//闰年多一天
				}
				int totalDay=0;
				int[] months= {
    
    31,towMonth,31,30,31,30,31,31,30,31,30,31};
				//前几个月加上本月的天数
				for(int i=0; i<months.length; i++) {
    
    
					if(month>=i+1) {
    
    
						if(month==i+1) {
    
    
							totalDay+=Integer.parseInt(strArr[2]);
							break;
						} else {
    
    
							totalDay+=months[i];
						}
					}
				}
				//输出结果
				System.out.println(totalDay);
			} catch (IOException e) {
    
    
				e.printStackTrace();
			}
		}