why does it queue has no member named push_back

Question

Why does it say it has no member?

void Tree::BFS(int row, int col, int src, int dest, int v, int pred[], int dist[]) {
    int num = board.get_checker_removed_num();
    int INT_MAX;
    if (num == 15) { return true; }//base case
    queue<int> q;//a queue to maintain queue of vertices
    bool *visited = new bool[v];// bool array to mark visited nodes
    for (int i = 0; i < v; i++) {//initialize starting value
        visited[i] = false;//nodes that has not been visited yet
        dist[i] = INT_MAX;//we use max int as initial distance, so we will not have any problems calculating min. distance
        pred[i] = -1;// node does not have pred.
    }
    int counter = 0;//intialize counter(to count how many nodes)
    visited[src] = true;//initialize values for starting src node
    dist[src] = 0;//first node from src to src is 0
    q.push_back(src);//add starting node into the queue
    counter++;//counter + 1 for every node that it goes thru
    while (!q.empty()) {//iterate to all elemements of the queue
        int u = q.front();//take front node from the queue
        q.pop_front();//remove node from list
        for (int i = 0; i < adj[u].size(); i++) {//Check all adjacent nodes for current node u
            if (visited[row][col] == false) {// If node is already visited we do not need to use it again
                visited[row][col] = true;// Mark node as visited
                dist[[row][col]] = dist[u] + 1;// Distance will increase with one
                pred[[row][col]] = u;
                q.push_back([row][col]);// Add the node at the end of the queue
                counter++;//for every node added, increase counter
                if ([row][col] = dest) { return true; }
            }
        }
    }
    return false;
}

error: 'class std::queue<int>' has no member named 'push_back'
error: 'class std::queue<int>' has no member named 'pop_front';

Because it doesn't. [Documentation](https://en.cppreference.com/w/cpp/container/queue). A `queue` is *not* a `vector`. — Michael Chourdakis, Jul 22 '19 at 03:20
`bool *visited = new bool[v];` -- Memory leak. Why didn't you use `std::vector visited(v);`? — PaulMcKenzie, Jul 22 '19 at 03:23
Avoid using std::vector: https://stackoverflow.com/questions/17794569/why-isnt-vectorbool-a-stl-container or see "effective STL" — Anonymous, Dec 02 '21 at 19:23

score 7 · Answer 1 · edited Jul 22 '19 at 08:21

7

If you use std::queue, the method should be q.push(x), q.front(), and q.pop().

edited Jul 22 '19 at 08:21

Piotr Siupa

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answered Jul 22 '19 at 03:32

Kevin Yang

79
4

why does it queue has no member named push_back

1 Answers1