Balanced Binary Tree, Leetcode 解题笔记

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.

这道题都说简单,在我看来其实未必,就是一道典型的递归,但是想面试中写对脑子还是要绕个弯的。

/**
 * Definition for binary tree
 * 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;
        if(Math.abs(getHeight(root.left) - getHeight(root.right)) > 1) return false;
        return isBalanced(root.left) && isBalanced(root.right);
    }
    
    public int getHeight(TreeNode root){
        if(root == null) return 0;
        return 1 + Math.max(getHeight(root.left), getHeight(root.right));
    }
}
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