Printing BFS (Binary Tree) in Level Order with Specific Formatting

Question

To begin with, this question is not a dup of this one, but builds on it.

Taking the tree in that question as an example,

    1 
   / \\
  2   3
 /            


        

Answer 1

A version that doesn't require extra storage:

std::deque bfs;
bfs.push_back(start);
int nodesInThisLayer = 1;
int nodesInNextLayer = 0;
while (!bfs.empty()) {
    Node front = bfs.front();
    bfs.pop_front();
    for (/*iterate over front's children*/) {
        ++nodesInNextLayer;
        nodes.push_back(child);
    }
    std::cout << node.value;
    if (0 == --nodesInThisLayer) {
        std::cout << std::endl;
        nodesInThisLayer = nodesInNextLayer; 
        nodesInNextLayer = 0;
    } else {
        std::cout << " ";
    }
}

P.S. sorry for the C++ code, I'm not very fluent in Python yet.