lintcode-medium-Balanced Binary Tree

Posted 2020-06-22 哥布林工程师

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.

 

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.

 

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root: The root of binary tree.
     * @return: True if this Binary tree is Balanced, or false.
     */
    public boolean isBalanced(TreeNode root) {
        // write your code here
        
        if(getDepth(root) != -1)
            return true;
        else 
            return false;
    }
    
    public int getDepth(TreeNode root){
        if(root == null)
            return 0;
        
        int left = getDepth(root.left);
        int right = getDepth(root.right);
        
        if(Math.abs(left - right) > 1)
            return -1;
        
        if(left == -1 || right == -1)
            return -1;
            
        return Math.max(left, right) + 1;
    }
}