A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.
CompleteBinary
lc#222 Count Complete Tree Nodes
compute the number of nodes in complete tree
public int countNodes(TreeNode root) {
if(root == null) return 0;
int height = 0;
TreeNode left = root.left, right = root.right;
while(left != null && right != null) {
height++;
left = left.left;
right = right.right;
}
return left == right ? (1 << height + 1) - 1 : 1 + countNodes(root.left) + countNodes(root.right);
}
