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Missing Number

Problem Description​

Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.

Example​

Example 1:

Input: nums = [3,0,1]
Output: 2
Explanation: n = 3 since there are 3 numbers, so all numbers are in the range [0,3]. 2 is the missing number in the range since it does not appear in nums.

Example 2:

Input: nums = [0,1]
Output: 2
Explanation: n = 2 since there are 2 numbers, so all numbers are in the range [0,2]. 2 is the missing number in the range since it does not appear in nums.

Constraints​

  • 1 <= n <= 104

Solution Approach​

Intuition:​

To efficiently determine the missing number in the array

Solution Implementation​

Code (C++):​

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int n = nums.size();
        int sum = (n*(n+1))/2;
        int s1=0;
        for(int i=0; i<n; i++){
             s1+=nums[i];
        }
        int ans = sum-s1;
        return ans;
    }
};