lintcode:Route Between Two Nodes in Graph

martin_liang

于 2015-05-17 23:00:50 发布

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分类专栏：算法 lintcode C++/C

本文链接：https://blog.youkuaiyun.com/martin_liang/article/details/45799451

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本文介绍了一种用于有向图中检测两个节点间是否存在路径的算法。通过广度优先搜索实现，确保了高效地找到从起点到终点的路径。文章提供了具体的代码实现，并附带示例说明算法的工作原理。

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Given a directed graph, design an algorithm to find out whether there is a route between two nodes.

Example

Given graph:

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

for s = B and t = E, return true

for s = D and t = C, return false

/**
 * Definition for Directed graph.
 * struct DirectedGraphNode {
 *     int label;
 *     vector<DirectedGraphNode *> neighbors;
 *     DirectedGraphNode(int x) : label(x) {};
 * };
 */
class Solution {
public:
    /**
     * @param graph: A list of Directed graph node
     * @param s: the starting Directed graph node
     * @param t: the terminal Directed graph node
     * @return: a boolean value
     */
    bool hasRoute(vector<DirectedGraphNode*> graph,
                  DirectedGraphNode* s, DirectedGraphNode* t) {
        // write your code here
        
        if (s->neighbors.size() == 0)
            return false;
            
        if (s == t)
            return true;
            
        deque<DirectedGraphNode *> bfs;
        
        bfs.push_back(s);
            
        while (bfs.size() > 0)
        {
            DirectedGraphNode* curNode = bfs[0];
            for (int i=0; i<curNode->neighbors.size(); i++)
            {
                if (curNode->neighbors[i] == t)
                {
                    return true;
                }
                else
                {
                    bfs.push_back(curNode->neighbors[i]);
                }
            }
            
            bfs.pop_front();
        }
        
        return false;
    }
};