leetcode692 Top K Frequent Words

思路：

堆。
实现：

#include <bits/stdc++.h>
using namespace std;

class Solution 
{
public:
    inline bool cmp(pair<int, string> a, pair<int, string> b)
    {
        if (a.first > b.first) return true;
        if (a.first == b.first && a.second < b.second) return true;
        return false;
    }
    struct cmp1
    {
        bool operator()(const pair<int, string>& a, const pair<int, string>& b) const
        {
            if (a.first > b.first) return true;
            if (a.first == b.first && a.second < b.second) return true;
            return false;
        }
    };
    vector<string> topKFrequent(vector<string>& words, int k) 
    {
        unordered_map<string, int> mp;
        for (auto it : words) mp[it]++;
        priority_queue<pair<int, string>, vector<pair<int, string>>, cmp1> q;
        int cnt = 0;
        for (auto it : mp)
        {
            pair<int, string> tmp(it.second, it.first);                
            if (cnt < k) 
            {
                q.push(tmp);                 
            }
            else if (cmp(tmp, q.top())) 
            { 
                q.push(tmp);                
                q.pop(); 
            }            
            cnt++;
        }
        vector<string> ret;
        while (!q.empty()) 
        {
            ret.push_back(q.top().second); q.pop(); 
        }        
        reverse(ret.begin(), ret.end());
        return ret;                     
    }
};
int main()
{
    vector<string> v = {"i", "love", "leetcode", "i", "love", "coding"};
    vector<string> ret = Solution().topKFrequent(v, 2);
    for (auto it : ret)
    {
        cout << it << " ";
    }
    cout << endl;
    return 0;
}