C language introduction practice (7): switch case calculation of days in the year (normal year / leap year calculation)

This is a 《C Language introduction practice 》 Series No 7 piece .
Last one ：C Language introduction practice (6)：int Pointer and adjacent comparison sorting

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subject

For any entered date （ Use variables for month, year and day respectively y、m、d Express ）, Find out the day of the year .

Tips

1. have access to switch Statement to realize the processing of different days in different months ;

2. In all case The order of matching constants and the method of calculating the number of days in each branch should be optimized as much as possible , For example, you can use multiple case Features of shared branch statements ;

3. 2 Days of the month , Need to consider whether leap year .

requirement

Example of input / output format 1：

Input ：2022 07 19< enter >
Output ：200

Example of input / output format 2：

Input ：2012 06 30< enter >
Output ：181

Pre knowledge

A hundred years ： Can be 400 Divided by leap years ; Not a whole century ： Can be 4 Divided by leap year .

Ordinary year 365 God , February is 28 God .

Leap year is 366 God , February is 29 God .

Reference code

#include <stdio.h>
int main() {
    
	//  For any entered date （ Use variables for month, year and day respectively y m d Express ）,
	//  Find out the day of the year .
	// 1/3/5/7/8/10/12 Month has 31 God 
	// 2 month , Ordinary year 28 God , Leap year 29 God 
	//  All other months 30 God 
	int y,m,d;
	scanf("%d %d %d", &y, &m, &d);
	//  Ordinary year 2 month 28 God  
	int daysInFebruary = 28;
	//  If it's a leap year , yes 29 God  
	if(y%400==0 || (y%100!=0 && y%4==0)) {
    
		daysInFebruary = 29;
	}
	
	// Cumulative results  
	int days = 0;
	int i;
	for(i=1;i<m;i++) {
    
		switch(i) {
    
			case 1:
			case 3:
			case 5:
			case 7:
			case 8:
			case 10:
				days += 31;
				break;
			case 2:
				days += daysInFebruary;
				break;
			default:
				days += 30;
				break;
		}
	}
	days += d;

	printf("%d", days);
	return 0;
}

Code duplicate

be familiar with switch-case Usage of , Note that each branch requires break.

The header file stdio.h Declarative scanf() and printf() It is used to process standard input and output in the standard library Library function .