lintcode-176-图中两个点之间的路线

176-图中两个点之间的路线

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。

样例

如下图:

for s = B and t = E, return true
for s = D and t = C, return false

标签

Cracking The Coding Interview 深度优先搜索 宽度优先搜索

思路

从 s 点开始对图进行遍历，若可以遍历到 t ，则 s 与 t 之间是否存在路线
这里使用了图的宽度优先遍历

code

/**
 * 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
        int size = graph.size(), i = 0;
        if (size <= 0) {
            return false;
        }
        queue<DirectedGraphNode*> queue;
        map<DirectedGraphNode*, bool> map;
        for (i = 0; i < size; i++) {
            map[graph[i]] = false;
            if (s == graph[i]) {
                queue.push(graph[i]);
            }
        }
        while (!queue.empty()) {
            DirectedGraphNode* node = queue.front();
            queue.pop();
            map[node] = true;
            if (node == t) {
                return true;
            }
            for (i = 0; i < node->neighbors.size(); i++) {
                if (map[node->neighbors[i]] == false) {
                    queue.push(node->neighbors[i]);
                }
            }
        }
        return false;
    }
};