lintcode-图中两个点之间的路线-176

来源：互联网发布：软件测试工程师难学不编辑：程序博客网时间：2024/05/21 14:08

给出一张有向图，设计一个算法判断两个点 s 与 t 之间是否存在路线。

如下图

A----->B----->C \     |  \    |   \   |    \  v     ->D----->E

for s = Band t = E, return true

for s = Dand t = C, return false

第一种解法 DFS

/** * Definition for Directed graph. * struct DirectedGraphNode { *     int label; *     vector<DirectedGraphNode *> neighbors; *     DirectedGraphNode(int x) : label(x) {}; * }; */class Solution {public:        map<DirectedGraphNode*,bool> vis;       bool dfs(DirectedGraphNode* s,DirectedGraphNode* t){        if(s==t)            return true;            for(auto e:s->neighbors){            if(vis[e])                continue;            vis[e]=true;                if(dfs(e,t))                return true;        }        return false;    }    bool hasRoute(vector<DirectedGraphNode*> graph,                  DirectedGraphNode* s, DirectedGraphNode* t) {        if(graph.empty())            return false;        return dfs(s,t);    }};

第二种解法 BFS

/** * Definition for Directed graph. * struct DirectedGraphNode { *     int label; *     vector<DirectedGraphNode *> neighbors; *     DirectedGraphNode(int x) : label(x) {}; * }; */class Solution {public:      bool hasRoute(vector<DirectedGraphNode*> graph,                  DirectedGraphNode* s, DirectedGraphNode* t) {                queue<DirectedGraphNode*> que;        map<DirectedGraphNode*,bool>  vis;        que.push(s);        vis[s]=true;        while(!que.empty()){            int len=que.size();            while(len--){                DirectedGraphNode* cur=que.front();                if(cur==t)                    return true;                que.pop();                for(auto e:cur->neighbors){                    if(vis[e])                        continue;                    que.push(e);                        vis[e]=true;                    }            }        }        return false;    }};

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