Java for LeetCode 222 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 2^h nodes inclusive at the last level h.

解题思路：

计算完全二叉树节点，直接递归会TLE，一个不错的思路是判断是否为满二叉树，然后进行递归，JAVA实现如下：

    public int countNodes(TreeNode root) {

        if(root==null)

        	return 0;

        int leftHeight=1,rightHeight=1;

        TreeNode temp=root.left;

        while(temp!=null){

        	temp=temp.left;

        	leftHeight++;

        }

        temp=root.right;

        while(temp!=null){

        	temp=temp.right;

        	rightHeight++;

        }

        if(leftHeight==rightHeight)

        	return (1<<leftHeight)-1;

        return countNodes(root.left)+countNodes(root.right)+1;

    }

巴特西

Java for LeetCode 222 Count Complete Tree Nodes

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