LeetCode——balanced-binary-tree

Question

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

递归遍历这棵树，然后求出子树左右孩子的高度差，如果大于1，那么返回false。 实现中定义了left，right，用于存储每一颗子树的左右子树的高度，max(left, right) + 1，是用于计算这颗子树的高度。

Code

/**
 * 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 = 0;
        return isBalanced_Solution(root, depth);
    }
    
    // 传引用保存每一颗子树的高度
    bool isBalanced_Solution(TreeNode* root, int& depth) {
        if (root == NULL) {
            depth = 0;
            return true;
        }
        
        int left,right;
        if (isBalanced_Solution(root->left, left) && isBalanced_Solution(root->right, right)) {
            int diff = abs(left - right);
            if (diff <= 1) {
                depth = max(left, right) + 1;
                return true;
            }
        }
        return false;
    }
};