Leetcode: Contains Duplicate (hash table)

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.

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 Array Hash Table

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Using hash table: map OR unordered_map.

Since we don't need the orders in the map, we can use unordered_map to speed up the process.

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