137. Single Number II.cpp

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ans = 0;
        map<int,int> m;
        int n = nums.size();
        for(int i=0;i<n;i++){
            m[nums[i]]++;
        }
        for(int i=0;i<n;i++){
            if(m[nums[i]]==1) return nums[i];
        }
        return 0;
    }
};