Snakeless path

#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;

const int MAXN = 100005;
vector<int> adj[MAXN];  // Adjacency list to store graph
int parent[MAXN];       // To track the path
bool visited[MAXN];     // To mark visited nodes

void bfs(int start, int end) {
    queue<int> q;
    q.push(start);
    visited[start] = true;
    parent[start] = -1;  // Start node has no parent

    while (!q.empty()) {
        int node = q.front();
        q.pop();

        if (node == end) return;  // If we reached the destination

        for (int neighbor : adj[node]) {
            if (!visited[neighbor]) {
                visited[neighbor] = true;
                parent[neighbor] = node;
                q.push(neighbor);
            }
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;

    // Reading the graph and snake paths
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

    // Perform BFS to find a path from 1 to n
    bfs(1, n);

    // If n is not visited, there's no path
    if (!visited[n]) {
        cout << 0 << endl;
    } else {
        // Reconstruct the path from n to 1 using the parent array
        vector<int> path;
        for (int v = n; v != -1; v = parent[v]) {
            path.push_back(v);
        }
        reverse(path.begin(), path.end());

        // Output the result
        cout << path.size() << endl;
        for (int v : path) {
            cout << v << " ";
        }
        cout << endl;
    }

    return 0;
}

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