Getting all nodes at a level in full binary tree, array format

Question

I need to get all the nodes at a certain level in a full binary tree from either the left or right subtree. I currently retrieve the binary tree from the DB as an array, for exa

Answer 1

// Adjust depth as needed
$depth = 3;

// using bit arithmetic. '<< 3' means multiply by 2 three times.
$start = 1 << $depth-1; // 1 * (2 * 2) because depth is 3
$end = (1 << $depth) -1; // 1 * (2 * 2 * 2) - 1

// if depth=3, this is [4,5,6,7]
$fullLevel = range($start, $end);

print_r($fullLevel);

if($depth > 1):
    $leftBranch = array_slice($fullLevel,0,count($fullLevel)/2);
    $rightBranch = array_slice($fullLevel,count($fullLevel) / 2);

    print_r($leftBranch); // [4,5]
    print_r($rightBranch); // [6, 7]
endif;