[LeetCode] 226. Invert Binary Tree - Java

https://leetcode.com/problems/invert-binary-tree/description/

Invert Binary Tree - LeetCode

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문제

Given the root of a binary tree, invert the tree, and return its root.

 

Example 1:

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]

Example 2:

Input: root = [2,1,3]
Output: [2,3,1]

Example 3:

Input: root = []
Output: []

 

Constraints:

• The number of nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

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풀이

풀이 과정

주어진 이진트리의 각 depth의 left와 right 노드를 뒤집는 문제이다.

재귀호출을 통하여 left와 right 노드를 서로 스왑하여 root 노드를 반환한다.

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최종 코드

/**
 * 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 TreeNode invertTree(TreeNode root) {
        // 노드가 없는 경우 탐색 종료
        if(root == null) return root;

        // left와 right 노드를 스왑
        TreeNode temp = root.left;
        root.left = invertTree(root.right);
        root.right = invertTree(temp);

        return root;
    }
}

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