Find the missing integer in an array if mean is given Last Updated : 20 Feb, 2023 Comments Improve Suggest changes Like Article Like Report Given an array of size N-1 and the mean of N elements (one element is not given). We need to find the missing value X in the array. Examples: Input : a[] = {2, 4, 20}, Mean = 9Output : Missing Element = 10 Explanation : Mean of (2, 4, 20, 10) is (2 + 4 + 20 + 10)/4 = 9 Let x be the missing element Mean = (a1 + a2 + a3.. + X + ..an)/N. So (a1 + a2 + a3.. + X + ..aN) = Mean*N . Missing element x = (Mean*N - (a1 + a2 + a3....aN)) Implementation: C++ // C++ program to find missing element in a // given array from mean. #include <bits/stdc++.h> using namespace std; // Size of a[] is N - 1 (one element missing) int findMissing(int a[], int N, int mean) { // Find sum of array elements int sum = 0; for (int i = 0; i < N - 1; i++) sum += a[i]; return (mean * N) - sum; } int main() { int a[] = {25, 65, 80}; int mean = 50; int n = sizeof(a)/sizeof(a[0]); cout << "The missing element : " << findMissing(a, n+1, mean) << endl; return 0; } Java // Java program to find missing element // in a given array from mean. import java.io.*; class GFG { // Size of a[] is N - 1 (one element missing) public static int findMissing(int a[], int N, int mean) { // Find sum of array elements int sum = 0; for (int i = 0; i < N - 1; i++) sum += a[i]; return (mean * N) - sum; } // Driver code public static void main (String[] args) { int a[] = {25, 65, 80}; int mean = 50; int n = a.length; System.out.println("The missing element : " + findMissing(a, n + 1, mean)); } } // This code is contributed by upendra bartwal Python3 # Python3 code to find missing element # in a given array from mean. # Size of a[] is N - 1 # (one element missing) def findMissing( a , N , mean ): # Find sum of array elements sum = 0 for i in range(N - 1): sum += a[i] return (mean * N) - sum # Driver Code a = [25, 65, 80] mean = 50 n = len(a) print("The missing element : ", end = '') print(findMissing(a, n+1, mean)) # This code is contributed by Sharad Bhardwaj. C# // C# program to find missing element // in a given array from mean. using System; class GFG { // Size of a[] is N - 1 // (one element missing) public static int findMissing(int[] a, int N, int mean) { // Find sum of array elements int sum = 0; for (int i = 0; i < N - 1; i++) sum += a[i]; return (mean * N) - sum; } // Driver code public static void Main() { int[] a = { 25, 65, 80 }; int mean = 50; int n = a.Length; Console.WriteLine("The missing element : " + findMissing(a, n + 1, mean)); } } // This code is contributed by vt_m. PHP <?php // PHP program to find missing // element in a given array // from mean. // Size of a[] is N - 1 // (one element missing) function findMissing($a, $N, $mean) { // Find sum of array elements $sum = 0; for ($i = 0; $i < $N - 1; $i++) $sum += $a[$i]; return ($mean * $N) - $sum; } // Driver Code $a = array(25, 65, 80); $mean = 50; $n = count($a); echo "The missing element : " .findMissing($a, $n + 1, $mean); // This code is contributed by Sam007 ?> JavaScript <script> // Javascript program to find // missing element in a // given array from mean. // Size of a[] is N - 1 // (one element missing) function findMissing( a, N, mean) { // Find sum of array elements let sum = 0; for (let i = 0; i < N - 1; i++) sum += a[i]; return (mean * N) - sum; } // Driver Code let a = [25, 65, 80]; let mean = 50; let n = a.length; document.write("The missing element : " + findMissing(a, n+1, mean) + "</br>"); </script> OutputThe missing element : 30 Time complexity: O(N) where N is no of the elements in the given array.Auxiliary space: O(1) since constant space is required. 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