Breadth First Search: Shortest Reach

• Time : O(v + e)
• Space : O(v + e)

c++

vector<int> bfs(int n, int m, vector<vector<int>> edges, int s) {
    vector<int> dis(n + 1, INT_MAX);
    dis[s] = 0;
    vector<int> adj[n + 1];
    for(auto& e : edges) {
        int u = e[0], v = e[1];
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    queue<int> q;
    q.push(s);
    while(!q.empty()) {
        auto u = q.front(); q.pop();
        for(auto& v : adj[u]) {
            if(dis[u] + 1 < dis[v]) {
                dis[v] = dis[u] + 1;
                q.push(v);
            }
        }
    }

    vector<int> res;
    for(int i = 1; i <= n; i++) {
        if(dis[i] == INT_MAX) res.push_back(-1);
        else if(dis[i] == 0) continue;
        else res.push_back(dis[i] * 6);
    }
    return res;
}