217. Contains Duplicate

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<int>& nums) {
        unordered_map<int, int> 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<Integer> set = new HashSet<Integer>();
        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	Accepted	28 ms	python
a few seconds ago	Accepted	13 ms	java
4 minutes ago	Accepted	24 ms	cpp