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Count Complete Tree Nodes
Given a complete binary tree, count the number of nodes.
Definition of a complete binary tree from Wikipedia:
In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * int val; 5 * TreeNode left; 6 * TreeNode right; 7 * TreeNode(int x) { val = x; } 8 * } 9 */ 10 public class Solution { 11 public int countNodes(TreeNode root) { 12 13 int leftDepth = leftDepth(root); 14 int rightDepth = rightDepth(root); 15 16 if (leftDepth == rightDepth) { 17 return (1 << leftDepth) - 1; 18 } 19 return 1 + countNodes(root.left) + countNodes(root.right); 20 21 } 22 23 private int rightDepth(TreeNode root) { 24 int depth = 0; 25 while (root != null) { 26 root = root.right; 27 depth++; 28 } 29 return depth; 30 } 31 32 private int leftDepth(TreeNode root) { 33 int depth = 0; 34 while (root != null) { 35 root = root.left; 36 depth++; 37 } 38 return depth; 39 } 40 }
Count Complete Tree Nodes
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