[LeetCode] 007: Balanced Binary Tree

最新推荐文章于 2022-11-11 21:06:11 发布

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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算法。对于该问题，高度平衡的二叉树定义为任意节点的左右子树深度之差不超过1。通过递归方式计算每个节点的左右子树高度，并检查它们之间的差值来实现。

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[Problem]

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.

[Solution]

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    // isBalanced
    bool isBalanced(TreeNode *root, int &height){
        // null node
        if(root == NULL){
            height = 0;
            return true;
        }
        
        // height of the left brunch and right brunch
        int leftH = 0, rightH = 0;
        bool left = isBalanced(root->left, leftH);
        bool right = isBalanced(root->right, rightH);
        
        // update height
        height = max(leftH, rightH) + 1;
        
        // balanced
        if(left && right && abs(leftH - rightH) <= 1){
            return true;
        }
        else{
            return false;
        }
    }
    
    // isBalanced
    bool isBalanced(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int height = 0;
        return isBalanced(root, height);
    }
};