PTA甲级 1107 Social Clusters (C++)_1107 social clusters c++-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_43659183/article/details/119927055

本文介绍了一种算法，用于在一个社交网络中识别并计算具有相同兴趣爱好的集群。通过输入每个人的爱好列表，程序能够找出所有的人群组，按人数降序显示。

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When register on a social network, you are always asked to specify your hobbies in order to find some potential friends with the same hobbies. A social cluster is a set of people who have some of their hobbies in common. You are supposed to find all the clusters.

Input Specification:

Each input file contains one test case. For each test case, the first line contains a positive integer $N (\leq 1000)$ , the total number of people in a social network. Hence the people are numbered from 1 to $N$ . Then $N$ lines follow, each gives the hobby list of a person in the format:
$K_i$ : $h_i$ [1] $h_i$ [2] … $h_i$ [ $K_i$ ]
where $K_i(>0)$ is the number of hobbies, and $h_i[j]$ is the index of the $j$ -th hobby, which is an integer in [1, 1000].

Output Specification:

For each case, print in one line the total number of clusters in the network. Then in the second line, print the numbers of people in the clusters in non-increasing order. The numbers must be separated by exactly one space, and there must be no extra space at the end of the line.

Sample Input:

Sample Output:

3
4 3 1

Caution:

写法属实有些复杂（不过竟然一遍就AC了hhhh）。

Solution:

// Talk is cheap, show me the code
// Created by Misdirection 2021-08-25 16:48:31
// All rights reserved.

#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>

using namespace std;

int main(){
    int n;
    scanf("%d", &n);
    vector<vector<int>> hobbis(1001), people(n + 1);

    for(int i = 0; i < n; ++i){
        int num, tmp;
        scanf("%d: ", &num);

        for(int j = 0; j < num; ++j){
            scanf("%d", &tmp);
            hobbis[tmp].push_back(i + 1);
            people[i + 1].push_back(tmp);
        }
    }

    vector<int> ans;
    vector<bool> p(n + 1, false), h(1001, false);

    int cnt = 0;

    for(int i = 0; i < 1000 & cnt < n; ++i){
        if(h[i + 1] == true) continue;

        int pos = 0;
        while(pos < hobbis[i + 1].size() && p[hobbis[i + 1][pos]] == true) pos++;
        if(pos == hobbis[i + 1].size()) continue;

        int tmpHobby = i + 1;
        int tmpPeople = hobbis[tmpHobby][pos];
        ans.push_back(1);
        p[tmpPeople] = true;
        cnt++;

        queue<int> q;
        for(int j = 0; j < people[tmpPeople].size(); ++j){
            if(h[people[tmpPeople][j]] == true) continue;
            q.push(people[tmpPeople][j]);
        }

        while(!q.empty()){
            int thisHobby = q.front();
            
            for(int j = 0; j < hobbis[thisHobby].size(); ++j){
                if(p[hobbis[thisHobby][j]] == true) continue;

                int thisPeople = hobbis[thisHobby][j];
                p[thisPeople] = true;
                ans[ans.size() - 1]++;

                for(int k = 0; k < people[thisPeople].size(); ++k){
                    if(h[people[thisPeople][k]] == true) continue;
                    q.push(people[thisPeople][k]);
                }
            }
            
            h[thisHobby] = true;
            q.pop();
        }
    }

    sort(ans.begin(), ans.end(), greater<int>());

    printf("%d\n", (int)ans.size());
    for(int i = 0; i < ans.size(); ++i){
        if(i == ans.size() - 1) printf("%d\n", ans[i]);
        else printf("%d ", ans[i]);
    }

    return 0;
}