To find Missing Number in an array

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To find Missing Number in an array

using Summation method

Given an array of size N-1 such that it only contains distinct integers in the range of 1 to N. Find the missing element.

Explanation :

  • Calculate the expected sum of all numbers from 1 to n using the formula: expected_sum = n * (n + 1) / 2.

  • Iterate through the array and calculate the actual sum of all the numbers.

  • missing number =actual sum - expected sum

  •        // function to find missing number in an array
        // n is range of integer from 1 to n
         int missingNumber(vector<int>& array, int n) {
                int actual_sum = n*(n+1)/2 ,arr_sum=0, miss_no;
                for(int i=0 ; i<n-1 ; i++){
                    arr_sum += array[i];
                }
                miss_no = actual_sum - arr_sum;
                return miss_no;
            }