package com.sky.pgm; public class MissingNumber { public static void main(String[] args) { int[] arr = {1, 2, 3, 5}; System.out.println(getMissingNumber(arr, 5)); } //To find one missing number public static int getMissingNumber(int[] arr, int totalCount) { int expectedSum = (int) (totalCount * ((float) (totalCount + 1) / 2)); int actualSum = 0; for (int i : arr) { actualSum += i; } return expectedSum - actualSum; } }