C++ Tricks

1. using v.emplace_back(i.second, i.first);
   instead of v.push_back(make_pair(i.second, i.first));

class Solution {
public:
    int minSetSize(vector<int>& arr) {
        unordered_map<int, int> m;
        for (int i : arr)
            m[i]++;
        vector<pair<int, int>> v;
        for (auto& i : m)
            v.emplace_back(i.second, i.first);
//instead of v.push_back(make_pair(i.second, i.first));
        sort(v.begin(), v.end());
        reverse(v.begin(), v.end());
            int ans = 0;
        int tmp = 0;
        for (auto i : v)
        {
            tmp += i.first * 2;
            ans++;
            if (tmp >= arr.size())break;
        }
        return ans;
    }
};