add: 一周中的第几天

Author: yi-ge

README.md

@@ -798,3 +798,7 @@ C++标准库提供的数据结构实在是太多了，参考[C++标准库头文
 - [参加考试的最大学生数](src/math/maximum_students_taking_exam.cpp)  [位运算, 数组, 动态规划, 状态压缩, 矩阵]
 
   - LeetCode 1349. 参加考试的最大学生数 <https://leetcode.cn/problems/maximum-students-taking-exam>
+
+- [一周中的第几天](src/math/day_of_the_week.cpp)  [数学]
+
+  - LeetCode 1185. 一周中的第几天 <https://leetcode.cn/problems/day-of-the-week>

images/math/day_of_the_week.jpeg

@@ -0,0 +1,24 @@
+// 一周中的第几天
+// https://leetcode.cn/problems/day-of-the-week
+// INLINE  ../../images/math/day_of_the_week.jpeg
+
+#include <headers.hpp>
+
+class Solution {
+public:
+  string dayOfTheWeek(int day, int month, int year) {
+    // 距离 1970 年 12 月 31 日有几天，再加上 3 后对 7 求余
+    vector<string> week = {"Monday", "Tuesday",  "Wednesday", "Thursday",
+                           "Friday", "Saturday", "Sunday"};
+    vector<int> monthDays = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30};
+    int days = 365 * (year - 1971) + (year - 1969) / 4;
+    for (int i = 0; i < month - 1; ++i) {
+      days += monthDays[i];
+    }
+    if (((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) && month > 2) {
+      days += day + 1;
+    }
+    days += day;
+    return week[(days + 3) % 7];
+  }
+};

src/math/day_of_the_week.cpp

@@ -1,4 +1,4 @@
-// 执行编译时间：2023-12-29 21:43:59
+// 执行编译时间：2023-12-30 13:30:33
 #include <gtest/gtest.h>
 #include <lib.hpp>
 

test/lib/lib_test.cpp

@@ -0,0 +1,22 @@
+#include <math/day_of_the_week.cpp>
+
+TEST(一周中的第几天, dayOfTheWeek) {
+  Solution solution;
+  // 示例 1：
+  // 输入：day = 31, month = 8, year = 2019
+  // 输出："Saturday"
+  int day = 31, month = 8, year = 2019;
+  EXPECT_EQ(solution.dayOfTheWeek(day, month, year), "Saturday");
+
+  // 示例 2：
+  // 输入：day = 18, month = 7, year = 1999
+  // 输出："Sunday"
+  day = 18, month = 7, year = 1999;
+  EXPECT_EQ(solution.dayOfTheWeek(day, month, year), "Sunday");
+
+  // 示例 3：
+  // 输入：day = 15, month = 8, year = 1993
+  // 输出："Sunday"
+  day = 15, month = 8, year = 1993;
+  EXPECT_EQ(solution.dayOfTheWeek(day, month, year), "Sunday");
+}