53 lines
1.6 KiB
C++
53 lines
1.6 KiB
C++
#include <iostream>
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#include <string>
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/**
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* #1185. Day of the Week
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* Given a date, return the corresponding day of the week for that date.
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* The input is given as three integers representing the day, month and year respectively.
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* Return the answer as one of the following values {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}.
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*
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* Input: day = 18, month = 7, year = 1999
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* Output: "Sunday"
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*
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* Range: year <- [1971, 2100]
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*/
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class Solution {
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private:
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inline static const std::string weekName[7] = {
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"Sunday",
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"Monday",
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"Tuesday",
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"Wednesday",
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"Thursday",
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"Friday",
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"Saturday"
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};
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inline static const int monthDays[12] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
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public:
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static std::string dayOfTheWeek(int day, int month, int year) {
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// Starts at 1969-01-01 [Wednesday]
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// (365 * 4 + 1) % 7 == 5, 365 % 7 == 1
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// 1969, +1 ~ +3 will not experience leap years.
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return weekName[(3 + (((year - 1969) >> 2) * 5) + ((year - 1969) & 3) + monthDays[month - 1] + day - 1 + (((year - 1969) & 3) == 3 && month > 2 && year != 2100 ? 1 : 0)) % 7];
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}
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};
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int main() {
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int n[12] {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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int ans, prev = 4;
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for (int y = 1971; y <= 2100; ++y) {
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for (int m = 1; m <= 12; ++m) {
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for (int d = 1; d <= ((!(y & 3) && m == 2 && y != 2100) ? 29 : n[m - 1]); ++d) {
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if ((ans = /* Solution::dayOfTheWeek(d, m, y) int when debug */ 0) != (prev = (prev + 1) % 7)) {
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std::printf("%d-%02d-%02d -> %d != %d\n", y, m, d, ans, prev);
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std::printf("ILLEGAL!\n");
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return 1;
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}
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}
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}
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}
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return 0;
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}
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