feat : added find majority element in array using Moore's Voting Algorithm

Author: Mrinal Chauhan

Diff for: Data-Structures/Array/MooreVotingAlgorithm.js

@@ -0,0 +1,33 @@
+/**
+ * Moore Voting Algorithm to find the majority element in an array
+ * Majority element is the one that appears more than n/2 times
+ * geeksforgeeks: https://www.geeksforgeeks.org/boyer-moore-majority-voting-algorithm/
+ * @param {Array} arr array of integers
+ * @returns {Number} majority element or null if no majority exists
+ */
+const MooreVotingAlgorithm = (arr) => {
+    let candidate = null;
+    let count = 0;
+  
+    // Phase 1: Finding the candidate
+    for (let num of arr) {
+      if (count === 0) {
+        candidate = num;
+        count = 1;
+      } else if (num === candidate) {
+        count++;
+      } else {
+        count--;
+      }
+    }
+  
+    // Phase 2: Validate the candidate
+    count = 0;
+    for (let num of arr) {
+      if (num === candidate) {
+        count++;
+      }
+    }
+  
+    return count > arr.length / 2 ? candidate : null;
+  };