Leetcode - Tree - Balanced Binary Tree

JerkWisdom

于 2014-08-14 16:18:33 发布

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分类专栏： Leetcode 文章标签： Tree

本文链接：https://blog.youkuaiyun.com/jonathan321/article/details/38560179

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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。通过递归计算每个节点的左右子树深度来实现。

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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.

/**
 * 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) {
        int depth;
        return checkBalanced(root, depth);
    }
    bool checkBalanced(TreeNode *root, int &depth) // 给checkBalanced传入depth是为了求depth的值，由于checkBalanced只能返回一个值，所以传入一个引用，求depth的值。
    {
        if(root==NULL)
        {
            depth=0;
            return true;
        }
        int depthLeft,depthRight;
        bool leftBalanced=checkBalanced(root->left, depthLeft);
        bool rightBalanced=checkBalanced(root->right, depthRight);
        depth=max(depthLeft+1,depthRight+1);
        return leftBalanced&&rightBalanced&&(abs(depthLeft-depthRight)<=1);
    }
};