g0301_0400.s0347_top_k_frequent_elements.Solution.cpp Maven / Gradle / Ivy

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104 LeetCode algorithm problem solutions

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// #Medium #Top_100_Liked_Questions #Array #Hash_Table #Sorting #Heap_Priority_Queue #Counting
// #Divide_and_Conquer #Quickselect #Bucket_Sort #Data_Structure_II_Day_20_Heap_Priority_Queue
// #Big_O_Time_O(n*log(n))_Space_O(k) #2024_05_22_Time_11_ms_(69.14%)_Space_16.3_MB_(88.53%)

#include 
#include 
#include 
using namespace std;

class Solution {
public:
    vector topKFrequent(vector& nums, int k) {
        sort(nums.begin(), nums.end());

        // Min heap of 
        priority_queue, vector>, greater>> minHeap;

        // Filter with min heap
        int j = 0;
        for (int i = 0; i <= nums.size(); ++i) {
            if (i == nums.size() || nums[i] != nums[j]) {
                minHeap.push({i - j, nums[j]});
                if (minHeap.size() > k) {
                    minHeap.pop();
                }
                j = i;
            }
        }

        // Convert to int array
        vector result(k);
        for (int i = k - 1; i >= 0; --i) {
            result[i] = minHeap.top().second;
            minHeap.pop();
        }

        return result;
    }
};