Create zeller-day-of-week-algorithm.cpp

Author: ps-19

zeller-day-of-week-algorithm.cpp

@@ -0,0 +1,30 @@
+class Solution {
+    bool isLeap(int year) {
+        return (year % 400 == 0) || (year % 4 == 0 && year % 100 != 0);
+    }
+    const string week[7] = {"Thursday", "Friday",  "Saturday", "Sunday", "Monday",   "Tuesday", "Wednesday"};
+public:
+    string dayOfTheWeek(int day, int month, int year) {
+        int days = 0;
+        for (int i = 1971; i < year; i++) {
+            if (isLeap(i)) {
+                days += 366;
+            } else {
+                days += 365;
+            }
+        }
+        for (int i = 1; i < month; i++) {
+            if (i == 2) {
+                if (isLeap(year)) {
+                    days += 29;
+                } else {
+                    days += 28;
+                }
+            }
+            else if (i == 4 || i == 6 || i == 9 || i == 11) days += 30;
+            else days += 31;
+        }
+        days += day;
+        return week[days % 7];
+    }
+};