code996/solutions/cpp/topKFrequentElements/solution.cpp at master · MingyiZhang/code996 · GitHub

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//
// Created by mingyi on 17.04.20.
//

#include <vector>
#include <unordered_map>
#include <queue>
#include <algorithm>
#include <iostream>

using namespace std;

vector<int> topKFrequent(vector<int> &nums, int k) {

  unordered_map<int, int> map;
  for (int num : nums) {
    map[num]++;
  }
  priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> q;
  int count = 0;
  for (const auto &p : map) {
    q.push({p.second, p.first});
    count++;
    if (count > k) {
      q.pop();
    }
  }
  vector<int> ret;
  for (int i = 0; i < k; i++) {
    ret.push_back(q.top().second);
    q.pop();
  }
  return ret;

//  // count
//  unordered_map<int, int> freqMap;
//  for (const auto &num : nums) {
//    freqMap[num]++;
//  }
//  // heapify
//  priority_queue<pair<int, int>> freqPQ;
//  for (const auto p : freqMap) {
//    freqPQ.push({p.second, p.first});
//  }
//
//  // get top K
//  vector<int> ret;
//  for (int i = 0; i < k; i++) {
//    ret.push_back(freqPQ.top().second);
//    freqPQ.pop();
//  }
//  return ret;
}

int main() {
  vector<int> nums1{1, 1, 1, 2, 2, 3};
  int k1{2};
  vector<int> result1 = topKFrequent(nums1, k1);
  for (const auto &v : result1) {
    cout << v << ' ';
  }
  return 0;
}