g0301_0400.s0347_top_k_frequent_elements.solution.go Maven / Gradle / Ivy

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package s0347_top_k_frequent_elements

// #Medium #Top_100_Liked_Questions #Top_Interview_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_03_16_Time_8_ms_(88.72%)_Space_6.2_MB_(61.53%)

import "sort"

type kvPair struct {
	Key   int
	Value int
}

func topKFrequent(nums []int, k int) []int {
	m := make(map[int]int)
	for _, v := range nums {
		if val, ok := m[v]; ok {
			m[v] = val + 1
		} else {
			m[v] = 1
		}
	}
	var pairs []kvPair
	for k, v := range m {
		pairs = append(pairs, kvPair{k, v})
	}

	sort.Slice(pairs, func(i, j int) bool {
		return pairs[i].Value > pairs[j].Value
	})

	var sortedKeys []int
	for _, pair := range pairs {
		sortedKeys = append(sortedKeys, pair.Key)
	}

	return sortedKeys[:k]
}