一、题目

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.

Example 1:

Input: nums = [1,2,3,1]
Output: true
Example 2:

Input: nums = [1,2,3,4]
Output: false
Example 3:

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

Constraints:

1 <= nums.length <= 105
-109 <= nums[i] <= 109

二、题解

class Solution {
public:bool containsDuplicate(vector<int>& nums) {unordered_map<int,int> map;for(auto x:nums){if(map[x] == 1) return true;map[x]++;}return false;}
};