Friend Circles

最新推荐文章于 2020-06-15 09:07:48 发布

原创最新推荐文章于 2020-06-15 09:07:48 发布 · 501 阅读

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本文介绍了一种使用深度优先搜索算法来计算班级中学生直接或间接朋友组成的社交圈子数量的方法。通过构建一个N×N的矩阵M来表示学生之间的友谊关系，并利用递归方式遍历每个未访问的学生节点来确定独立的社交圈子。

There are N students in a class. Some of them are friends, while some are not. Their friendship is transitive in nature. For example, if A is a direct friend of B, and B is a direct friend of C, then A is an indirect friend of C. And we defined a friend circle is a group of students who are direct or indirect friends.

Given a N*N matrix M representing the friend relationship between students in the class. If M[i][j] = 1, then the i_th and j_th students are direct friends with each other, otherwise not. And you have to output the total number of friend circles among all the students.

class Solution {
public:
    int findCircleNum(vector<vector<int>>& M) {

    	int s = 0;
    	int n = M.size();
    	bool visit[n];
    	memset(visit,0,n);

        for(int j = 0; j < n; j ++)
        {
        	if(visit[j] == 0)
        	{
        		s ++;
        		dfs(j, M, visit);
        	}
        }
        return s;
    }
private:
        void dfs(int i,vector<vector<int>>& M,bool* visit) 
        {
            visit[i] = 1;
        	for(int j = 0; j < M.size(); j ++)
        	{
        		if(M[i][j] == 1 && i != j && visit[j] == 0)
        		{
        			dfs(j, M, visit);
        		}
        	}
        } 
};