LeetCode-110-Balanced Binary Tree(平衡二叉树)

Q:

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.

Analysis:

使用递归计算树的高度，若当前结点满足平衡二叉树性质，仍需要判断该结点的左右子树是否满足平衡二叉树。

Code:

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public boolean isBalanced(TreeNode root) {        if (root == null) {            return true;        }        int left = deep(root.left);        int right = deep(root.right);        // 若本节点满足平衡二叉树，判断左右子树是否满足        if (Math.abs(left - right) <= 1) {            return isBalanced(root.left) && isBalanced(root.right);        } else {            return false;        }    }    public static int deep(TreeNode root) {        int depthLeft, depthRight;        if (root == null) {            return 0;        }        if (root.right == null && root.left == null) {            return 1;        } else {            depthLeft = deep(root.left);            depthRight = deep(root.right);        }        return 1+(depthLeft>depthRight?depthLeft:depthRight);    }}