# Find the Duplicate Number LeetCode Solution

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

## 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

## Find the Duplicate Number SolutionC++

``````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;
}
};```Code language: PHP (php)```

## Find the Duplicate Number SolutionJava

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

## Find the Duplicate Number SolutionJavaScript

``````var findDuplicate = function(nums) {
const seen = new Set();
for (const num of nums) {
if (seen.has(num)) {
return num;
}
}
return -1;
};```Code language: JavaScript (javascript)```

## Find the Duplicate Number SolutionPython

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