Sunday, 13 January 2019

Java Program to find the Missing Number in an Array

        This is one of the basic java coding interview questions. In interview, they will give an integer array from 1 to n and each number of array can not be duplicate. They will ask to write the java code to find the missing number of an array.

For Example:-

int[] numbers = {1,3,5,4,2,8,7}; 
Missing number is 6.

MissingNumber.java,

package com.sample;

public class MissingNumber {
 
        public static void main(String[] args) {
  
                  int[] numbers = {1,4,2,5,3,6,7,9}; 
                  int totalNumbers = numbers.length + 1;
  
                  System.out.println("Total numbers - "+totalNumbers);
  
                    // first to calculate the sum of total numbers
  
                   int sumOfTotalNumbers = (totalNumbers * (totalNumbers + 1)) / 2;
  
                   // find the sum of given array. 
  
                   int sumOfArrayNumbers = 0;
  
                   for (int i=0; i<numbers.length; i++) {
                            sumOfArrayNumbers = sumOfArrayNumbers + numbers[i];
                   }
  
                   int missingNumber = sumOfTotalNumbers - sumOfArrayNumbers;
  
                   System.out.println("Missing number - "+missingNumber);
         }

}

Output:--
Total numbers - 9
Missing number - 8



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