LeetCode 110: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.

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

//解决思路：利用两个递归，一个递归求树的高度，另一个递归求左右树是否平衡。
class Solution {
public:
	bool isBalanced(TreeNode* root) {
		if (root == NULL)
		{
			return true;
		}
		else
		{
			int lH = getHeight(root->left);
			int rH = getHeight(root->right);

			if (lH - rH <= 1 && lH - rH >= -1)
			{
				return isBalanced(root->left) && isBalanced(root->right);
			}
			else
				return false;
		}
	}

	int getHeight(TreeNode* root){
		if (root == NULL)
		{
			return 0;
		}
		else
		{
			if (root->left == NULL)
			{
				return getHeight(root->right) + 1;
			}
			else if (root->right == NULL)
			{
				return getHeight(root->left) + 1;
			}
			else
			{
				int l = getHeight(root->left);
				int r = getHeight(root->right);
				return l < r ? (r + 1) : (l + 1);
			}
		}
	}
};