leetcode-放松题-一周中的第几天

package algorithm.dayOfTheWeek;

/**
 * 1185. 一周中的第几天
 * 给你一个日期，请你设计一个算法来判断它是对应一周中的哪一天。
 *
 * 输入为三个整数：day、month 和 year，分别表示日、月、年。
 *
 * 您返回的结果必须是这几个值中的一个 {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}。
 *
 *
 *
 * 示例 1：
 *
 * 输入：day = 31, month = 8, year = 2019
 * 输出："Saturday"
 * 示例 2：
 *
 * 输入：day = 18, month = 7, year = 1999
 * 输出："Sunday"
 * 示例 3：
 *
 * 输入：day = 15, month = 8, year = 1993
 * 输出："Sunday"
 *
 *
 * 提示：
 *
 * 给出的日期一定是在 1971 到 2100 年之间的有效日期。
 */
public class dayOfTheWeek {
    public static String dayOfTheWeek(int day, int month, int year) {

        String[] week = {"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
        int[] monthDays = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30};
        //计算到今年多少天，加上闰年的
        int days = 365 * (year-1971)+(year-1969)/4;
        //计算这个月的
        for (int i = 0; i < month-1; i++) {
            days+=monthDays[i];
        }
        if(year%400==0 ||(year %4==0 &&year%100!=0)){
           days+=1;
        }
        //计算这个月过了几天
        days+=day;
        //1971.1.1是星期五就行了,+3转化成周一
        return week[(days+3)%7];
    }

    public static void main(String[] args) {
        int day = 17, month = 1, year = 2022;
        System.out.println(dayOfTheWeek(day,month,year));
    }
}