Balanced Binary Tree

Description

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.

Example
Given binary tree 
A = {3,9,20,#,#,15,7}, 
B = {3,#,20,15,7}
A)  3            B)    3 
   / \                  \
  9  20                 20
    /  \                / \
   15   7              15  7
The binary tree A is a height-balanced binary tree, but B is not.

Link

Lintcode_ladder

Method

1. x
2. x

Example

1. 1

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
class Solution {
public:
    /**
     * @param root: The root of binary tree.
     * @return: True if this Binary tree is Balanced, or false.
     */
    bool isBalanced(TreeNode *root) {
        // write your code here
        return get_maxdepth(root) != -1;
    }
private:
    int get_maxdepth(TreeNode* root){
        if (!root) {
            return 0;
        }
        int left = get_maxdepth(root->left);
        int right = get_maxdepth(root->right);
        // find unbalanced subtree
        if (left == -1 || right == -1 || abs(left - right) > 1 ) {
           return -1; 
        }
        return max(left, right) + 1;
    }
};

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