chore(java): add majority element (#354)

algorithms/Java/README.md

@@ -6,6 +6,7 @@
 2. [Kadanes Algorithm](arrays/kadanes-algorithm.java)
 3. [Left Rotation](arrays/left-rotation.java)
 4. [Unique Digits of Large Number](arrays/unique-digits-of-large-number.java)
+5. [Majority Element](arrays/majority-element.java)
 
 ## Graphs
 

algorithms/Java/arrays/majority-element.java

@@ -0,0 +1,70 @@
+//Given an array A of N elements. Find the majority element in the array.
+//A majority element in an array A of size N is an element that appears more than N/2 times in the array
+
+// Moore’s Voting Algorithm => Time Complexity: O(n), Space Complexity: O(1)
+
+import java.util.*;
+import java.io.*;
+import java.lang.*;
+
+class Main {
+    public static void main(String args[]) {
+        Scanner sc = new Scanner(System.in);
+        int t = sc.nextInt();
+        
+        while(t-- > 0) {
+            int n =sc.nextInt();
+            int arr[] = new int[n];
+            
+            for(int i = 0; i < n; i++)
+             arr[i] = sc.nextInt();
+             
+           System.out.println(new Solution().majorityElement(arr, n)); 
+        }
+    }
+}
+
+class Solution
+{
+    static int majorityElement(int a[], int size){
+        int cand = findCand(a, size);
+        if(isMajority(a, size, cand))
+            return cand;
+        return -1;
+    }
+    
+    static int findCand(int arr[], int n){
+        int max_index=0; int count=1;
+        for(int i=1; i<n; i++){
+            if(arr[max_index]==arr[i])
+                count++;
+            else count--;
+            if(count==0){
+                max_index=i;
+                count=1;
+            }
+        }
+        return arr[max_index];
+    }
+    
+    static boolean isMajority(int arr[], int n, int cand){
+        int count=0;
+        for(int i=0; i<n; i++){
+            if(cand==arr[i])
+                count++;
+        }
+        if(count > n/2) return true;
+        return false;
+    }
+}
+
+/* Test Case: 
+Input:
+N = 5  A[] = {3,1,3,3,2} 
+
+Output: 3
+
+Explanation:
+Since, 3 is present more
+than N/2 times, so it is 
+the majority element. */