CareerCup 4.2

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;}