1107. Social Clusters (30) -- 简单 DFS / BFS

题目地址

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

题目描述

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

ac

这题就直接dfs，用变量标记某个人是否已经访问过

注意结果可能包含重复的
比如

44 3 3 1

• multiset
• 或者直接vector 然后再sort排序

ac1, DFS

#include <cstdio>#include <cstdlib>#include <cmath>#include <cstring>#include <iostream>#include <string>#include <vector>#include <queue>#include <algorithm>#include <sstream>#include <stack> #include <map> #include <set> #include <unordered_map>using namespace std;const int INF = 0x7fffffff;const int MIN_INF = - INF -1;typedef long long int LL;const int N = 1001;int n;vector<int> hobbys[N];vector<int> persons[N];bool vis[N];int cnt;void dfs(int index,int depth){    //cout << index << endl;    cnt ++;    int len = persons[index].size();    for(int i=0;i<len;i++)    {        int h = persons[index][i];        int lenh = hobbys[h].size();        for(int j=0;j<lenh;j++)        {            int perh = hobbys[h][j];            if(perh != index && !vis[perh])            {                vis[perh] = true;                dfs(perh,depth + 1);            }        }    }}int main(){    //freopen("in.txt","r",stdin);    while(scanf("%d", &n) != EOF)    {        for(int i=0;i<N;i++)        {            hobbys[i].clear();            persons[i].clear();            vis[i] = false;        }        int k,h;        for(int i=0;i<n;i++)        {            scanf("%d:", &k);            for(int j = 0;j<k;j++)            {                scanf("%d",&h);                persons[i+1].push_back(h);                hobbys[h].push_back(i+1);            }        }        vector<int> ans;        for(int i=1;i<=n;i++)        {            if(vis[i] == false)            {                vis[i] = true;                cnt = 0;                dfs(i,1);                ans.push_back(cnt);            }        }        int len = ans.size();        sort(ans.begin(), ans.end());        printf("%d\n",len);        for(int i= len-1;i>0;i--)        {            printf("%d ", ans[i]);        }        printf("%d\n", ans[0]);    }    //printf("\n");    return 0;}

ac2, BFS

#include <cstdio>#include <cstdlib>#include <cmath>#include <cstring>#include <iostream>#include <string>#include <vector>#include <queue>#include <algorithm>#include <sstream>#include <list>#include <stack> #include <map> #include <set> #include <iterator> #include <unordered_map>using namespace std;const int INF = 0x7fffffff;typedef long long int LL;const int N = 1000 + 5;int n;vector<int> hobby[N];vector<int> hpo[N];bool vis[N];int bfs(int id){  int cnt = 1;  queue<int> que;  que.push(id);  while(!que.empty())  {    int tid = que.front();    que.pop();    int tHobbysSize = hobby[tid].size();    for(int i=0;i<tHobbysSize;i++)    {      int th = hobby[tid][i];      int othersSize = hpo[th].size();      for(int j = 0;j < othersSize; j ++)      {        int oId = hpo[th][j];        if(vis[oId] == false)        {          que.push(oId);          vis[oId] = true;          cnt ++;        }      }    }  }  return cnt;}bool cmp(int a, int b){  return a > b;}int main(){  //freopen("in.txt", "r" , stdin);  while(scanf("%d", &n) != EOF)  {    for(int i=1;i<=n;i++)    {      int k;      scanf("%d: ", &k);      while(k--)      {        int tmp;        scanf("%d", &tmp);        hobby[i].push_back(tmp);        hpo[tmp].push_back(i);      }    }    for(int i=1;i<=n;i++)    {      vis[i] = false;    }    vector<int> ans;    int ansLen = 0;    for(int i=1;i<=n;i++)    {      if(vis[i] == false)      {        vis[i] = true;        int cnt = bfs(i);        ans.push_back(cnt);        ansLen ++;      }    }    if(ansLen > 1)      sort(ans.begin(), ans.end(), cmp);    printf("%d\n", ansLen);    printf("%d", ans[0]);    for(int i=1;i<ansLen;i++)    {      printf(" %d", ans[i]);    }    printf("\n");  }  return 0;}