1107. Social Clusters (30)

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时间限制

1000 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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 (<=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:

Ki: hi[1] hi[2] ... hi[Ki]

where Ki (>0) is the number of hobbies, and hi[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:

8

3: 2 7 10

1: 4

2: 5 3

1: 4

1: 3

1: 4

4: 6 8 1 5

1: 4

Sample Output:

3

4 3 1

C++:

递归法：

/*
 @Date    : 2018-02-23 21:28:59
 @Author  : 酸饺子 ([email protected])
 @Link    : https://github.com/SourDumplings
 @Version : $Id$
*/

/*
https://www.patest.cn/contests/pat-a-practise/1107
 */

#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <array>

using namespace std;

static const int MAXK = 1001;
static const int MAXN = 1001;
static array<vector<int>, MAXK> hobbyData;
static vector<int> clusters;
static int N;
static bool checked[MAXN];

void find_friends(vector<vector<int>> &people, int p)
{
    checked[p] = true;
    ++clusters.back();
    for (int h : people[p])
    {
        for (int f : hobbyData[h])
        {
            if (!checked[f])
                find_friends(people, f);
        }
    }
    return;
}

int main(int argc, char const *argv[])
{
    scanf("%d", &N);
    vector<vector<int>> people(N);
    fill(checked, checked+N, false);
    int Ki, h;
    for (int i = 0; i != N; ++i)
    {
        scanf("%d:", &Ki);
        for (int j = 0; j != Ki; ++j)
        {
            scanf("%d", &h);
            people[i].push_back(h);
            hobbyData[h].push_back(i);
        }
    }
    for (int p = 0; p != N; ++p)
    {
        if (!checked[p])
        {
            clusters.push_back(0);
            find_friends(people, p);
        }
    }
    sort(clusters.rbegin(), clusters.rend());
    printf("%d\n", clusters.size());
    int output = 0;
    for (auto i : clusters)
    {
        if (output++) putchar(' ');
        printf("%d", i);
    }
    putchar('\n');
    return 0;
}

并查集：

/*
 @Date    : 2018-09-04 22:11:54
 @Author  : 酸饺子 ([email protected])
 @Link    : https://github.com/SourDumplings
 @Version : $Id$
*/

/*
https://pintia.cn/problem-sets/994805342720868352/problems/994805361586847744
 */

#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

int N;
const int MAXN = 1005;
int root[MAXN];
vector<int> peopleHobbies[MAXN], hobbyPeople[MAXN];

int get_root(int p)
{
    if (root[p] < 0)
        return p;
    else
        return get_root(root[p]);
}

void my_union(int p1, int p2)
{
    int r1 = get_root(p1), r2 = get_root(p2);
    if (r1 != r2)
    {
        if (root[r1] <= root[r2])
        {
            root[r1] += root[r2];
            root[r2] = root[p2] = r1;
        }
        else
        {
            root[r2] += root[r1];
            root[r1] = root[p1] = r2;
        }
    }
    return;
}

int main()
{
    scanf("%d", &N);
    for (int i = 0; i != N; ++i)
    {
        root[i] = -1;
        int K;
        scanf("%d:", &K);
        for (int j = 0; j != K; ++j)
        {
            int h;
            scanf("%d", &h);
            peopleHobbies[i].push_back(h);
            hobbyPeople[h].push_back(i);
        }
    }
    for (int i = 0; i != N; ++i)
    {
        for (int h : peopleHobbies[i])
        {
            for (int p : hobbyPeople[h])
            {
                if (p != i)
                    my_union(i, p);
            }
        }
    }
    vector<int> res;
    for (int i = 0; i != N; ++i)
    {
        if (root[i] < 0)
            res.push_back(-root[i]);
    }
    sort(res.begin(), res.end());
    printf("%d\n", res.size());
    int output = 0;
    for (auto it = res.rbegin(); it != res.rend(); ++it)
    {
        if (output++)
            putchar(' ');
        printf("%d", *it);
    }
    putchar('\n');
    return 0;
}