LeetCode | Balanced Binary Tree

题目

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

这题用递归写很方便了，下面的代码里，getHeight函数的返回值为-1时，表示不是平衡树了，可以一直回退返回结果。

代码

public class BalancedBinaryTree {
	public boolean isBalanced(TreeNode root) {
		if (root == null) {
			return true;
		}
		return getHight(root) != -1;
	}

	private int getHight(TreeNode root) {
		if (root == null) {
			return 0;
		}
		int leftHeight = getHight(root.left);
		int rightHeight = getHight(root.right);
		if (leftHeight == -1 || rightHeight == -1
				|| Math.abs(leftHeight - rightHeight) > 1) {
			return -1;
		}
		return Math.max(leftHeight, rightHeight) + 1;
	}
}