zoukankan      html  css  js  c++  java
  • #Leetcode# 692. Top K Frequent Words

    https://leetcode.com/problems/top-k-frequent-words/

    Given a non-empty list of words, return the k most frequent elements.

    Your answer should be sorted by frequency from highest to lowest. If two words have the same frequency, then the word with the lower alphabetical order comes first.

    Example 1:

    Input: ["i", "love", "leetcode", "i", "love", "coding"], k = 2
    Output: ["i", "love"]
    Explanation: "i" and "love" are the two most frequent words.
        Note that "i" comes before "love" due to a lower alphabetical order.
    

    Example 2:

    Input: ["the", "day", "is", "sunny", "the", "the", "the", "sunny", "is", "is"], k = 4
    Output: ["the", "is", "sunny", "day"]
    Explanation: "the", "is", "sunny" and "day" are the four most frequent words,
        with the number of occurrence being 4, 3, 2 and 1 respectively.
    

    Note:

    1. You may assume k is always valid, 1 ≤ k ≤ number of unique elements.
    2. Input words contain only lowercase letters.

    Follow up:

    1. Try to solve it in O(n log k) time and O(n) extra space.

    代码:

    class Solution {
    public:
        vector<string> topKFrequent(vector<string>& words, int k) {
            vector<string> res(k);
            unordered_map<string, int> freq;
            auto cmp = [](pair<string, int>& a, pair<string, int>& b) {
                return a.second > b.second || (a.second == b.second && a.first < b.first);
            };
            priority_queue<pair<string, int>, vector<pair<string, int>>, decltype(cmp) > q(cmp);
            for (auto word : words) ++freq[word];
            for (auto f : freq) {
                q.push(f);
                if (q.size() > k) q.pop();
            }
            for (int i = res.size() - 1; i >= 0; --i) {
                res[i] = q.top().first; q.pop();
            }
            return res;
        }
    };
    

      priority_queue 自定义排序 get    priority_queue 正常按照第一项从大到小 然后第二项从大到小就不符合题意需要第二项按从小到大 所以自定义

  • 相关阅读:
    图论4-floyd
    。。。
    [LOJ10164]数字游戏
    KMP模板
    无向图割点模板
    tarjan有向图模板
    LCA倍增模板
    P2149 [SDOI2009]Elaxia的路线
    树的直径dp模板
    [暑假集训]Day4 T3 平板涂色
  • 原文地址:https://www.cnblogs.com/zlrrrr/p/10340161.html
Copyright © 2011-2022 走看看