unordered_map的應用

961. N-Repeated Element in Size 2N Array

Easy

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In a array ​

​A​

​​ of size ​

​2N​

​​, there are ​

​N+1​

​ unique elements, and exactly one of these elements is repeated N times.

Return the element repeated ​

​N​

​ times.

Example 1:

Input: [1,2,3,3]

Output: 3

Example 2:

Input: [2,1,2,5,3,2]

Output: 2

Example 3:

class Solution {
public:
    int repeatedNTimes(vector<int>& A) {
        unordered_map<int,int> Map;
        int Result;
        for(int i = 0;i < A.size();i ++){
            Map[A[i]] ++;
        }
        int len = A.size();
        int Half = len / 2;
        for(auto it = Map.begin();it != Map.end();it ++){
            if(it->second == Half){
                Result = it->first;
            }
        }
        return Result;
    }
};