[LeetCode]Balanced Binary Tree

最新推荐文章于 2017-06-28 16:04:50 发布

原创最新推荐文章于 2017-06-28 16:04:50 发布 · 657 阅读

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#Java #LeetCode #Depth-first search #Tree

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本文介绍了一种用于判断二叉树是否为高度平衡的方法。高度平衡二叉树定义为对于树中每一个节点，其两个子树的深度相差不超过1。文章通过递归方式实现了树的深度计算，并据此判断整棵树是否符合平衡条件。

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.

Tree Depth-first Search

/**
 * 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(depth(root)!=-1) return true;
        return false;
    }
    
    private int depth (TreeNode root){
    	if(root==null) return 0;
    	int left = 0;
    	int right = 0;
    	if(root.left!=null) {
    		left = depth(root.left);
    	}
    	if(root.right!=null) {
    		right = depth(root.right);
    	}
    	if(left<0||right<0||Math.abs(right-left)>1) return -1;
    	return Math.max(depth(root.left),depth(root.right))+1;
    }
}