Array: Missing Number in n

Author: harshbhardwaj

Leetcode/src/com/practise/MissingNumbers.java

@@ -0,0 +1,45 @@
+package com.practise;
+/*
+Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.
+
+        Example 1:
+
+        Input: [3,0,1]
+        Output: 2
+        Example 2:
+
+        Input: [9,6,4,2,3,5,7,0,1]
+        Output: 8
+        Note:
+        Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?
+*/
+
+public class MissingNumbers {
+    public int missingNumber(int[] nums) {
+
+        int actualSum = 0;
+        int largest=0;
+        int expectedSum =0;
+
+
+        for (int i=0;i< nums.length;i++){
+            if(nums[i] > largest){
+                largest = nums[i];
+            }
+        }
+
+        if(nums.length > largest) {
+            expectedSum = nums.length*(nums.length +1)/2;
+        }else{
+            expectedSum = largest*(largest + 1)/2;
+        }
+
+
+
+        for (int i=0;i< nums.length;i++){
+            actualSum = actualSum + nums[i];
+        }
+
+        return expectedSum - actualSum;
+    }
+}