Invert Binary Tree

Author: wad-jangjaejeong

invert-binary-tree/jaejeong1.java

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+/**
+ * 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 {
+  // 풀이: child node로 내려가면서 재귀로 계속 left와 right를 바꿔준다.
+  // TC: O(N)
+  // SC: O(N)
+  public TreeNode invertTree(TreeNode root) {
+    return invert(root);
+  }
+
+  private TreeNode invert(TreeNode node) {
+    if (node == null) {
+      return node;
+    }
+
+    node = swap(node);
+
+    invert(node.left);
+    invert(node.right);
+
+    return node;
+  }
+
+  private TreeNode swap(TreeNode node) {
+    var temp = node.left;
+    node.left = node.right;
+    node.right = temp;
+
+    return node;
+  }
+}