LeetCode547朋友圈，使用并查集和图的搜索

1、使用并查集

class DisjoinSet{
    private:
        vector<int>_id; //元素对应的集合，根
        vector<int>_size; //集合大小    
        int _count; //集合个数
    public:
        DisjoinSet(int n){ //初始化成n个集合
            for(int i = 0;i < n;i++){
                _id.push_back(i);
                _size.push_back(1);
            }
            _count = n;
        }
        //查
        int _find(int p){
            while(p!=_id[p]){
                _id[p] = _id[_id[p]];
                p = _id[p];
            }
            return p;
        }
        //并，小规模向大规模上合并，提高查询效率
        void _union(int p,int q){
            int i = _find(p);
            int j = _find(q);
            if(i == j)
                return;
            if(_size[i]<_size[j]){
                _id[i] = j;
                _size[j] += _size[i];
            }
            else{
                _id[j] = i;
                _size[i] += _size[j];
            }
            _count--;
        }
    int count(){
        return _count;
    }
    };
class Solution {
public:
    int findCircleNum(vector<vector<int>>& M) {
     DisjoinSet ds(M.size());
        for(int i = 0;i<M.size();i++)
        {
            for(int j = i+1;j<M.size();j++)
                if(M[i][j])
                    ds._union(i,j);
        }
        return ds.count();
    }
};

2、深度优先搜索图

void DFS_circle(int n,vector<vector<int>>& graph,vector<int>& visit)
{
    visit[n] = 1;
    for(int i = 0;i<graph[n].size();i++)
        if(visit[i] == 0 && graph[n][i] == 1)
            DFS_circle(i,graph,visit);
}
//朋友圈
int findCircleNum(std::vector<std::vector<int>>& M)
{
    //图的搜索
    vector<int>visit(M.size(),0);
    int count = 0;
    for(int i = 0;i<M.size();i++)
    {
        if(visit[i]==0)
        {
            DFS_circle(i,M,visit);
            count++;
        }
    }
    return count;
}