leetcode 110 Balanced Binary Tree ----- java

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.

 

判断一棵树是否是平衡二叉树

 

利用高度的答案，递归求解。

/**
 * 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 = maxDepth(root.left);
        int right = maxDepth(root.right);

        if( left - right > 1 || right - left > 1)
            return false;
        return isBalanced(root.left)&&isBalanced(root.right);

        
    
    }

    public int maxDepth(TreeNode root) {
        if( root == null )
            return 0;
        if( root.left == null && root.right == null)
            return 1;
        if( root.left == null)
            return maxDepth(root.right)+1;
        if( root.right == null)
            return maxDepth(root.left)+1;
        return Math.max(maxDepth(root.left),maxDepth(root.right))+1;}
}