Balanced Binary Tree

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.

C++版本1：

#include <iostream>
#include <vector>
#include <stdlib.h>

using namespace std;
struct TreeNode{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x):val(x),right(NULL),left(NULL){}
};

class Solution{
private:
    bool balanced=true;
    int height(TreeNode *root){
      if(!balanced){
        return -1;
      }
      if(root==NULL){
        return 0;
      }
      int leftH,rightH;
      leftH=height(root->left)+1;
      rightH=height(root->right)+1;
      if(abs(leftH-rightH)>1){
        balanced=false;
      }
      return leftH>rightH?leftH:rightH;
    }
    bool isBalanced(TreeNode *root){
        balanced=true;
        height(root);
        return balanced;
    }
};

int main()
{
    cout << "Hello world!" << endl;
    return 0;
}

　　c++版本2：

/**
 * 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 checkBalance(TreeNode *node, int &dep)
    {
        if (node == NULL)
        {
            dep = 0;
            return true;
        }
        
        int leftDep, rightDep;
        bool leftBalance = checkBalance(node->left, leftDep);
        bool rightBalance = checkBalance(node->right, rightDep);
        
        dep = max(leftDep, rightDep)+1;
        
        return leftBalance && rightBalance && (abs(rightDep - leftDep) <= 1);
    }
    
    bool isBalanced(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int dep;
        return checkBalance(root, dep);
    }
};

　　Java版本：

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
   public boolean isBalanced(TreeNode root) {
		if (root == null)
			return true;
 
		if (getHeight(root) == -1)
			return false;
 
		return true;
	}
 
	public int getHeight(TreeNode root) {
		if (root == null)
			return 0;
 
		int left = getHeight(root.left);
		int right = getHeight(root.right);
 
		if (left == -1 || right == -1)
			return -1;
 
		if (Math.abs(left - right) > 1) {
			return -1;
		}
 
		return Math.max(left, right) + 1;
 
	}
}