Leetcode 树 Balanced Binary Tree

最新推荐文章于 2019-06-30 00:31:29 发布

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最新推荐文章于 2019-06-30 00:31:29 发布

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Balanced Binary Tree

Total Accepted: 13700 Total Submissions: 42780

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.

题意：给定一棵二叉树，判断它是不是高平衡的。高平衡指的是每一个节点的左右子树的深度差不超过1
思路：bfs递归
1.如果根节点的左右子树深度之差大于1，返回false
2.如果左子树或右子树不是平衡的，返回false
3.返回true
复杂度：时间O(n)，空间O(log n)

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isBalanced(TreeNode *root){
        if(!root) return true;
    	if (abs(depth(root->left) - depth(root->right)) > 1) return false;
    	return isBalanced(root->left) && isBalanced(root->right);
    }
    
    int depth(TreeNode *root){
    	if(!root) return 0;
    	int left_depth = depth(root->left);
    	int right_depth = depth(root->right) ;
    	return left_depth > right_depth ? left_depth + 1 : right_depth + 1;
    }
};