leetcode/docs/solutions/(array)/217-contains-duplicate.mdx

---
title: '217. Contains Duplicate'
description: Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct
sidebar:
  label: 'Contains Duplicate'
  badge: 'Easy'
---

<Badge variant="accent">Hash Table</Badge>

### Example 1:
- Input: `nums = [1,2,3,1]`
- Output: `true`
- Explanation: The element `1` occurs at the indices `0` and `3`.

### Example 2:
- Input: `nums = [1,2,3,4]`
- Output: `false`
- Explanation: All elements are distinct.

### Example 3:
- Input: `nums = [1,1,1,3,3,4,3,2,4,2]`
- Output: `true`

### Constraints:

- `1 <= nums.length <= 10^5`
- `-10^9 <= nums[i] <= 10^9`

## Solution

```js
/**
 * @param {number[]} nums
 * @return {boolean}
 */
var containsDuplicate = function(nums) {
  const freq = {};
  for (let n of nums) {
    freq[n] = (freq[n] || 0) + 1;
    if (freq[n] >= 2) {
      return true;
    }
  } 
  return false;
};
```