###### Write a Program to find duplicate number between 1 to N Numbers

This article will help you to understand “Java Program to find duplicate number.”

Here we have an array from 1 to N with one duplicate number.

e.g we have array from 1 to 10 and 2 is repeated once in this array. Then we need to find that 2 is a duplicate number in given array.

###### Java Program to find duplicate number between 1 to N Numbers

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package com.codenuclear; public class FindDuplicateNumber { public int findDuplicateNumber(int inputArray[],int N){ int sum = getSum(inputArray); int dupNo = sum - (N*(N+1)/2); return dupNo; } public int getSum(int numbers[]){ int sum = 0; for(int num:numbers){ sum += num; } return sum; } public static void main(String args[]){ int N = 10; // Below array is from 1 to 10 and 2 is repeated once. int givenArray[] = {5,2,9,8,2,3,10,1,7,6,4}; FindDuplicateNumber obj = new FindDuplicateNumber (); System.out.println("Duplicate Number is : "+obj.findDuplicateNumber(givenArray,N)); } } |

Output

{1,2,3,2,5} => dublicate 2 is not coming as output

Hi Prasanna,

You are missing 4 in your array modify your array and check once.