邻接矩阵表示法创建有向图

以邻接矩阵表示法创建有向图，并基于图的深度优先遍历策略设计一算法，判断有向图中是否存在由顶点A到顶点B的路径。

#include <iostream>
#include <stack>
#include <cstring>

struct Graph {
    int v_num; // 顶点数
    int** adj_matrix; // 邻接矩阵
};

bool has_path(Graph* graph, int A, int B) {
    if (A == B) {
        return true;
    }

    // 深度优先遍历
    bool visited[graph->v_num];
    memset(visited, false, graph->v_num * sizeof(bool));
    std::stack<int> s;
    s.push(A);
    visited[A] = true;

    while (!s.empty()) {
        int curr = s.top();
        s.pop();
        for (int i = 0; i < graph->v_num; i++) {
            if (graph->adj_matrix[curr][i] && !visited[i]) {
                if (i == B) {
                    return true;
                }
                s.push(i);
                visited[i] = true;
            }
        }
    }

    return false;
}

Graph* create_graph() {
    Graph* graph = new Graph;
    graph->v_num = 5;
    graph->adj_matrix = new int*[graph->v_num];
    for (int i = 0; i < graph->v_num; i++) {
        graph->adj_matrix[i] = new int[graph->v_num];
        memset(graph->adj_matrix[i], 0, graph->v_num * sizeof(int));
    }
    graph->adj_matrix[0][1] = 1;
    graph->adj_matrix[0][2] = 1;
    graph->adj_matrix[1][3] = 1;
    graph->adj_matrix[2][3] = 1;
    graph->adj_matrix[3][4] = 1;
    return graph;
}

int main() {
    Graph* graph = create_graph();
    int A = 0, B = 4;
    if (has_path(graph, A, B)) {
        std::cout << "There is a path from vertex " << A << " to vertex " << B << "." << std::endl;
    } else {
        std::cout << "There is no path from vertex " << A << " to vertex " << B << "." << std::endl;
    }
    return 0;
}