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);
    }

}