[코테 풀이] Balanced Binary Tree

Q_110) Balanced Binary Tree

출처 : https://leetcode.com/problems/balanced-binary-tree/submissions/

Given a binary tree, determine if it is height-balanced.

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

🙈 풀이 참조한 문제
1) countHeight()의

if (countHeight(root.right) == -1 
|| countHeight(root.left) == -1){
 	return -1;
}

코드는 :
현재 노드를 기준으로 각 오른쪽 subtree와 왼쪽 subtree가 balanced인지
아닌지 여부를 확인

2) countHeight()의

 if(Math.abs(countHeight(root.right)-countHeight(root.left))>1){
 	return -1;
}

코드는 :
현재 노드가 balanced인지 아닌지 여부를 확인

3) countHeight()의

return Math.max(countHeight(root.right), 
				countHeight(root.left)) + 1;

코드는 :
balanced인 경우, 현재 노드의 height를 구함