Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

Input: [1,2,3,1]Output: true

Example 2:

Input: [1,2,3,4]Output: false

Example 3:

Input: [1,1,1,3,3,4,3,2,4,2]Output: true

 

Approach #1: C++.

class Solution {public:    bool containsDuplicate(vector
     
      & nums) {        unordered_map
      
        mp;        for (int i = 0; i < nums.size(); ++i) {            mp[nums[i]]++;            if (mp[nums[i]] > 1) return true;        }        return false;    }};
      
     

　　

Approach #2: Java.

class Solution {    public boolean containsDuplicate(int[] nums) {        Set
     
       set = new HashSet
      
       ();        for (int i : nums)            if (!set.add(i))                return true;        return false;    }}
      
     

　　

Approach #3: Python.

class Solution(object):    def containsDuplicate(self, nums):        """        :type nums: List[int]        :rtype: bool        """        return len(nums) != len(set(nums))

　　

Time Submitted	Status	Runtime	Language
a few seconds ago		28 ms	python
a few seconds ago		13 ms	java
4 minutes ago		24 ms	cpp