CareerCup 4.2

最新推荐文章于 2018-04-04 17:51:00 发布

原创最新推荐文章于 2018-04-04 17:51:00 发布 · 529 阅读

0 ·

CC 4.0 BY-SA版权

CareerCup 150 专栏收录该内容

30 篇文章

订阅专栏

本文介绍了一种用于判断有向图中两个节点间是否存在路径的算法——广度优先搜索（BFS）。通过使用队列结构，该算法能够有效地遍历图中的所有节点，并确保每个节点仅被访问一次。文章还提供了一个示例代码，展示了如何初始化图节点状态，并利用BFS算法检查特定起点到终点的连通性。

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

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

struct GraphNode {
    enum State {unvisited, visited, visiting} state;
    vector<GraphNode*> adjacentNodes;
    GraphNode(void) : state(unvisited) {}
};

void initNodeState(vector<GraphNode> &g) {
    for (GraphNode &node : g) {
        node.state = GraphNode::unvisited;
    }
}

bool BFS(GraphNode *a, GraphNode *b) {
    queue<GraphNode*> q;
    a->state = GraphNode::visiting;
    q.push(a);
    while (!q.empty()) {
        GraphNode *curr = q.front();
        q.pop();
        for (GraphNode *next : curr->adjacentNodes) {
            if (next->state == GraphNode::unvisited) {
                if (next == b) {
                    return true;
                } else {
                    next->state = GraphNode::visiting;
                    q.push(next);
                }
            }
        }
    }
    return false;
}

int main() {
    vector<GraphNode> g(4);
    g[0].adjacentNodes.push_back(&g[1]);
    g[1].adjacentNodes.push_back(&g[2]);
    initNodeState(g);
    if (BFS(&g[0], &g[2])) {
        cout << "Connected" << endl;
    }
    return 0;
}