MissingNumber.java

package com.sarvesh.javabasics;

import java.util.Scanner;

public class MissingNumber {

 public static void main(String[] args) {

 Scanner sc = new Scanner(System.in);

 System.out.print("Enter no of elements: ");
 int n = sc.nextInt();

 int[] arr = new int[n - 1];
 System.out.println("Enter elements:");
 for (int i=0;i<n-1;i++) {
 arr[i] = sc.nextInt();
 }

 int expected = n*(n + 1)/2;
 int real = 0;
 for (int i=0;i<arr.length;i++) {
 real += arr[i];
 }
 int missing = expected - real;
 System.out.println("Missing number is: " + missing);

 sc.close();
 }
}