文章作者：Tyan 部落格：noahsnail.com  |  CSDN  |  簡書

1. Description

2. Solution

• Version 1

/**
 *  Definition for a binary tree node.
 *  struct TreeNode {
 *      int val;
 *      TreeNode *left;
 *      TreeNode *right;
 *      TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 *  };
 **/
class Solution {
 

public:
    bool isBalanced(TreeNode* root) {
        if(!root) {
            return true;
        }
        int left = getDepth(root->left);
        int right = getDepth(root->right);
        if(abs(left - right) > 1) {
            return false;
        }
        return isBalanced(root->
 
left) && isBalanced(root->right);
    }

private:
    int getDepth(TreeNode* root) {
        if(!root) {
            return 0;
        }
        return max(getDepth(root->left), getDepth(root->right)) + 1;
    }
};

• Version 2

/**
 *  Definition for a binary tree node.
 *  struct TreeNode {
 *      int val;
 *      TreeNode *left;
 *      TreeNode *right;
 *      TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 *  };
 **/
 

class Solution {
public:
    bool isBalanced(TreeNode* root) {
        return checkBalance(root) != -1;
    }

private:
    int checkBalance(TreeNode* root) {
        if(!root) {
            return 0;
        }
        int left = checkBalance(root->left);
        if(left == -1) {
            return -1;
        }
        int right = checkBalance(root->right);
        if(right == -1) {
            return -1;
        }
        if(abs(left - right) > 1) {
            return -1;
        }
        return max(left, right) + 1;
    }
};

Reference