题解 | #小红书推荐系统#

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <sstream>
#include <algorithm>

using namespace std;

// 自定义排序的比较函数
bool compare(const pair<string, int>& a, const pair<string, int>& b) {
    if (a.second != b.second) {
        return a.second > b.second; // 按频次降序
    }
    return a.first < b.first; // 频次相同，按字典序升序
}

int main() {
    string line;
    getline(cin, line);
    stringstream ss(line);
    string word;
    
    // 1. 词频统计
    map<string, int> counts;
    while (ss >> word) {
        counts[word]++;
    }
    
    // 2. 关键词筛选
    vector<pair<string, int>> keywords;
    for (auto const& [key, val] : counts) {
        if (val >= 3) {
            keywords.push_back({key, val});
        }
    }
    
    // 3. 自定义排序
    sort(keywords.begin(), keywords.end(), compare);
    
    // 4. 输出结果
    for (const auto& p : keywords) {
        cout << p.first << '\n';
    }
    
    return 0;
}

import java.util.Scanner;
import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String line = sc.nextLine();
        String[] words = line.split("\\s+");
        
        // 1. 词频统计
        Map<String, Integer> counts = new HashMap<>();
        for (String word : words) {
            counts.put(word, counts.getOrDefault(word, 0) + 1);
        }
        
        // 2. 关键词筛选
        List<Map.Entry<String, Integer>> keywords = new ArrayList<>();
        for (Map.Entry<String, Integer> entry : counts.entrySet()) {
            if (entry.getValue() >= 3) {
                keywords.add(entry);
            }
        }
        
        // 3. 自定义排序
        Collections.sort(keywords, (a, b) -> {
            if (!a.getValue().equals(b.getValue())) {
                return b.getValue().compareTo(a.getValue()); // 按频次降序
            }
            return a.getKey().compareTo(b.getKey()); // 频次相同，按字典序升序
        });
        
        // 4. 输出结果
        for (Map.Entry<String, Integer> entry : keywords) {
            System.out.println(entry.getKey());
        }
    }
}

import sys
from collections import Counter

def solve():
    # 读取和分割输入
    words = sys.stdin.readline().strip().split()
    
    # 1. 词频统计
    counts = Counter(words)
    
    # 2. 关键词筛选
    keywords = []
    for word, count in counts.items():
        if count >= 3:
            keywords.append((word, count))
            
    # 3. 自定义排序
    # Python的sort/sorted可以接受一个元组作为key，依次比较元组中的元素
    # 我们让频次取负数，即可实现降序排序
    keywords.sort(key=lambda x: (-x[1], x[0]))
    
    # 4. 输出结果
    for word, count in keywords:
        print(word)

solve()