C语言 计算某年某月某日在该年的第几天

废话不多说，上代码

通过传入year，month，day来获取天数

int getDay(int y, int m, int d) {
	int rtnDay = d;
	int day[] = { 31, 28, 31, 30, 31, 30, 31, 31,30, 31, 30 };
	int moon = !(y % 4) && y % 100 || !(y % 400);
	day[1] = 28 + moon;
	for (size_t i = 0; i < m - 1; i++) {
		rtnDay += day[i];
	}
	return rtnDay;
}

通过定义结构体返回天数
首先定义一个Date结构体

typedef struct Date {
	int year;
	int month;
	int day;
} Date;

然后是结构体版的代码

int getDay(Date * d) {
	int rtnDay = d->day;
	int day[] = { 31, 28, 31, 30, 31, 30, 31, 31,30, 31, 30 };
	int moon = !(d->year % 4) && d->year % 100 || !(d->year % 400);
	day[1] = 28 + moon;
	for (size_t i = 0; i < d->month - 1; i++) {
		rtnDay += day[i];
	}
	return rtnDay;
}

总代码

#include <stdio.h>

typedef struct Date {
	int year;
	int month;
	int day;
} Date;

int getDay(Date * d);

int main() {
	Date d = { 2013, 3, 1 };
	printf("%d\n", getDay(&d));

	return 0;
}

int getDay(Date * d) {
	int rtnDay = d->day;
	int day[] = { 31, 28, 31, 30, 31, 30, 31, 31,30, 31, 30 };
	int moon = !(d->year % 4) && d->year % 100 || !(d->year % 400);
	day[1] = 28 + moon;
	for (size_t i = 0; i < d->month - 1; i++) {
		rtnDay += day[i];
	}
	return rtnDay;
}