---
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
icon: dot
topics:
  - { name: "Array", slug: "array" }
  - { name: "Hash Table", slug: "hash-table" }
  - { name: "Sorting", slug: "sorting" }
video: "3OamzN90kPg"
issue: "https://github.com/prdlk/leetcode/issues/27"
sidebar:
  label: 'Contains Duplicate'
  badge: 'Easy'
---

### 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`

## Approach

```mermaid
flowchart TD
  S(["containsDuplicate(nums)"]) --> I["freq = {}"]
  I --> L{"more n in nums?"}
  L -- no --> E(["return false"])
  L -- yes --> C["freq[n] = (freq[n] or 0) + 1"]
  C --> Q{"freq[n] >= 2?"}
  Q -- yes --> R(["return true"])
  Q -- no --> L
```

## Solution

```py
class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        return len(set(nums)) != len(nums)
```