Day of Week 九度教程第7题 求某一天是周几

题目链接
题目大意：
输入一个日期，要求输出该日期为星期几。

解题思路：
先确定原点日期，然后我们只需要求出所给的日期与今天的日期相隔了几天，将差值对7求余数，再根据今天是星期几，便能得出答案。
AC代码:

#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
using namespace std;
#define isyeap(x) (x % 100 !=0 && x % 4 == 0 ) || x % 400 == 0 ? 1 : 0
struct date {
    int year;string month;int day;
};
int daysofmonth[2][13] = {
     {
     0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
{
     0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } };
string month[12] = {
     "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
string week[7] = {
     "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
int count(date a) {
    int mycount = 0;for (int i = 0; i < a.year; i++) {
    if (isyeap(i)) mycount += 366;else mycount += 365;}int thismonth;for (int i = 0; i < 12; i++) {
    if (month[i] == a.month) {
    thismonth = i + 1 ;break;}}for (int i = 0; i < thismonth; i++) {
    if (isyeap(a.year)) {
    mycount += daysofmonth[0][i];}else mycount += daysofmonth[1][i];}mycount += a.day;return mycount;
}
int main() {
    date today;today.year = 2019;today.month = "September";today.day = 2;int todayofweek = 1;int num2 = count(today);date a;while (cin>>a.day>>a.month>>a.year) {
    int num1 = count(a);int num3 = (num1 - num2);int t = ((num3 % 7) + 7) % 7;cout << week[t] << endl;}return 0;
}