[LeetCode] Balanced Binary Tree

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.

根据平衡二叉树的定义，左右子树的最大高度差不超过1，且左右子树也是平衡二叉树

/**
 * 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) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(root == NULL) return true;
        int maxLeft = maxHeight(root->left);
        int maxRight = maxHeight(root->right);
        if(abs(maxLeft-maxRight) > 1) return false;
        return isBalanced(root->left) && isBalanced(root->right);
    
    }

    int maxHeight(TreeNode *root) {
        if(root == NULL) return 0;
        int maxLeft = maxHeight(root->left);
        int maxRight = maxHeight(root->right);
        return (maxLeft > maxRight ? maxLeft+1 : maxRight+1);
    }
};