Last updated on October 5th, 2024 at 05:36 pm

Here, We see Find the Duplicate Number LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

List of all LeetCode Solution

Find the Duplicate Number LeetCode Solution

Problem Statement

Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive.

There is only one repeated number in nums, return this repeated number.

You must solve the problem without modifying the array nums and uses only constant extra space.

Example 1:
Input: nums = [1,3,4,2,2]
Output: 2

Example 2:
Input: nums = [3,1,3,4,2]
Output: 3

Example 3:
Input: nums = [3,3,3,3,3]
Output: 3

1. Find the Duplicate Number Solution C++

class Solution {
public:
    int findDuplicate(vector<int>& nums) {
        std::unordered_set<int> seen;
        for (int num : nums) {
            if (seen.find(num) != seen.end()) {
                return num;
            }
            seen.insert(num);
        }
        return -1;
    }
};

2. Find the Duplicate Number Solution Java

class Solution {
    public int findDuplicate(int[] nums) {
        HashSet<Integer> seen = new HashSet<>();
        for (int num : nums) {
            if (seen.contains(num)) {
                return num;
            }
            seen.add(num);
        }
        return -1;        
    }
}

3. Find the Duplicate Number Solution JavaScript

var findDuplicate = function(nums) {
    const seen = new Set();
    for (const num of nums) {
        if (seen.has(num)) {
            return num;
        }
        seen.add(num);
    }
    return -1;    
};

4. Find the Duplicate Number Solution Python

class Solution(object):
    def findDuplicate(self, nums):
        seen = set()
        for num in nums:
            if num in seen:
                return num
            seen.add(num)