Count Complete Tree Nodes

Given a complete binary tree, count the number of nodes.

完全二叉树，就是除了叶结点都有两个结点。如果左右子树的高度相同，

结点个数为2^h-1。否则可以遍历左右子树的结点和+1.

public int countNodes(TreeNode root) {
	int count=0;
	int left=leftHeight(root);
	int right=rightHeight(root);
	if(left==right)
		return (1<<left)-1;
	return countNodes(root.left)+countNodes(root.right)+1;
}
private int leftHeight(TreeNode node){
	if(node==null)
		return 0;
	int height=0;
	while(node!=null){
		height++;
		node=node.left;
	}
	return height;
}
private int rightHeight(TreeNode node){
	if(node==null)
		return 0;
	int height=0;
	while(node!=null){
		height++;
		node=node.right;
	}
	return height;
}