Balanced Binary Tree

描述​

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.

代码​

// Balanced Binary Tree// 时间复杂度O(n)，空间复杂度O(logn)public class Solution {    public boolean isBalanced (TreeNode root) {        return balancedHeight (root) >= 0;    }    /**     * Returns the height of root if root is a balanced tree,     * otherwise, returns -1.     */    private static int balancedHeight (TreeNode root) {        if (root == null) return 0;  // 终止条件        int left = balancedHeight (root.left);        int right = balancedHeight (root.right);        if (left < 0 || right < 0 || Math.abs(left - right) > 1) return -1;  // 剪枝        return Math.max(left, right) + 1; // 三方合并    }}