【LeetCode】Balanced Binary Tree

标签：leetcode   二叉树   

      题意：

     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.

     思路：

     判断一棵二叉树是否是平衡的，只要递归判断左右子树的高度。如果左右子树不再平衡，那么改变条件变量，递归返回。

      代码：

      C++：

/**
 * 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) {
        height(root);
        return flag;
    }
private:
    bool flag = true;

    int height(TreeNode* root)
    {
        if(!flag) return -1;

        if(!root) return 0;

        int l = height(root->left);
        int r = height(root->right);

        if(abs(l - r) > 1) flag = false;

        return (l>r?l:r) + 1;
    }

};

     Python:

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    # @param root, a tree node
    # @return a boolean
    def isBalanced(self, root):
        self.flag = True
        self.height(root)
        return self.flag

    def height(self,root):
        if not self.flag:
            return -1

        if not root:
            return 0

        l = self.height(root.left)
        r = self.height(root.right)

        if abs(l-r) > 1:
            self.flag = False

        return max(l,r)+1

【LeetCode】Balanced Binary Tree

标签：leetcode   二叉树   

原文地址：http://blog.csdn.net/jcjc918/article/details/44487393