采用邻接表存储结构，不是邻接矩阵的形式，编写一个判别无向图中任意给定的两个顶点之间是否存在一条长度为k的简单路径的算法，用C语言伪代码编写，注释用英文给出

// Check if there exists a simple path of length k between two given vertices in an undirected graph using adjacency list representation
/*
adj[]: adjacency list of the graph
visited[]: array to keep track of visited vertices
src: source vertex
dest: destination vertex
k: length of the required path
*/
bool isSimplePath(vector<int> adj[], bool visited[], int src, int dest, int k) {
    // if the length of the required path is 0, return true if source and destination are same, else false
    if (k == 0) {
        return (src == dest);
    }
    // mark the current vertex as visited
    visited[src] = true;
    // traverse all the adjacent vertices of the current vertex
    for (int i = 0; i < adj[src].size(); i++) {
        // if the adjacent vertex is not visited
        if (!visited[adj[src][i]]) {
            // recursively check if there exists a simple path of length k-1 between the adjacent vertex and the destination vertex
            if (isSimplePath(adj, visited, adj[src][i], dest, k-1)) {
                return true;
            }
        }
    }
    // mark the current vertex as unvisited
    visited[src] = false;
    // if no simple path of length k is found, return false
    return false;
}