Java solution "Find the Duplicate Number "

Bit-Manipulation/Java/10_Find_the_Duplicate_Number.java

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+// Question  https://leetcode.com/problems/find-the-duplicate-number/
+
+/**
+ * first of all find the max number in num[],
+ * then create an array of size (max_nums + 1).
+ * finally find out the first repetition number using frequency method,
+ * if frequency of any number == 2 then return false else true.
+ */
+
+// Solution
+
+import java.util.Scanner;
+
+class Solution {
+    public static int findDuplicate(int[] nums) {
+        int n = -1;
+
+        for(int i = 0; i < nums.length; i++)
+            n = Math.max(n,nums[i]);
+
+        int[] arr = new int[n+1];
+
+        for(int i = 0; i < nums.length; i++){
+            arr[nums[i]]++;
+            if(arr[nums[i]] == 2)
+                return nums[i];
+        }
+        return -1;
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        int n = sc.nextInt();
+        int[] nums = new int[n];
+
+        for(int i = 0; i < n; i++)
+            nums[i] = sc.nextInt();
+
+        System. out.println( findDuplicate(nums) );
+    }
+}
+
+// Examples
+/**
+ * Example 1:
+ * Input: nums = [1,3,4,2,2]
+ * Output: 2
+ *
+ * Example 2:
+ * Input: nums = [3,1,3,4,2]
+ * Output: 3
+ */