1000324. 前 K 个高频元素

难度: Medium

题目描述

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解题思路

代码实现

解决方案

java

 

import java.util.*;

class Solution {
    public int[] topKFrequent(int[] nums, int k) {

        Map<Integer, Integer> map = new TreeMap<>();

        // 统计频率
        for (int i = 0; i < nums.length; i++) {
            map.put(nums[i], map.getOrDefault(nums[i], 0) + 1);
        }
        // 获取topk
        ArrayList<Map.Entry<Integer, Integer>> list = new ArrayList<>();

        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {

            if (list.size() == 0) {
                list.add(entry);
            } else {
                Integer index = null;
                for (int i = 0; i < list.size(); i++) {
                    if (list.get(i).getValue() < entry.getValue()) {
                        index = i;
                        break;
                    }
                }
                if (index == null) {
                    list.add(entry);
                } else {
                    list.add(index, entry);
                }

            }
            if (list.size() == k + 1) {
                list.remove(k);
            }
        }

        return list.stream().mapToInt(Map.Entry<Integer, Integer>::getKey).toArray();

    }
}