BFS Vector Pseudocode

func sumTreeBFS(vector<int>& tree) {
    if (tree is empty):
      return 0

    queue<int> q;
    q.push(0); 

    sum = 0;

    while (q not empty {
        int index = q.front();
        q.pop();

        sum += tree[index];

        leftIndex = 2 * index + 1;
        rightIndex = 2 * index + 2;

        ....
        
        ....
    }

    return sum;
}