You are given the following information, but you may prefer to do some research for yourself.
- 1 Jan 1900 was a Monday.
- Thirty days has September,
April, June and November.
All the rest have thirty-one,
Saving February alone,
Which has twenty-eight, rain or shine.
And on leap years, twenty-nine. - A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
#include <stdio.h> #include <stdbool.h> const int a[2][12] = {{31,28,31,30,31,30,31,31,30,31,30,31}, {31,29,31,30,31,30,31,31,30,31,30,31}}; bool leapYear(int n) //判断闰年 { return (((n % 4 ==0) && (n % 100 !=0)) || (n % 400 == 0)); } bool issunday(int n) //判断某天是否是星期天 { return (n % 7 == 0 ? true : false); } void solve(void) { int num, i, j, count; count = 0; i = 1901; num = 1; while(i < 2000) { int t = (leapYear(i) ? 1 : 0); //判断闰年 for(j = 0; j < 12; j++) { num += a[t][j]; if(issunday(num)) count++; } i++; } printf("%d\n",count); } int main(void) { solve(); return 0; }
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Answer:
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171 |