[juhui-jeong] WEEK 10 Solutions

invert-binary-tree/juhuj-jeong.java

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+/*
+이전 풀이
+ * 시간 복잡도: O(n)
+ * 공간 복잡도: O(n)
+ */
+public class Solution {
+    public TreeNode invertTree(TreeNode root) {
+        if (root == null) {
+            return null;
+        }
+
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.offer(root);
+
+        while (!queue.isEmpty()) {
+            TreeNode cur = queue.poll();
+
+            TreeNode temp = cur.left;
+            cur.left = cur.right;
+            cur.right = temp;
+
+            if (cur.left != null) {
+                queue.offer(cur.left);
+            }
+
+            if (cur.right != null) {
+                queue.offer(cur.right);
+            }
+        }
+
+        return root;
+    }
+}
+
+/**
+ * 시간 복잡도: O(n)
+ * 공간 복잡도: O(n)
+ * DFS 풀이
+ */
+class Solution {
+    public TreeNode invertTree(TreeNode root) {
+        if (root == null) return null;
+
+        Deque<TreeNode> stack = new ArrayDeque<>();
+        stack.push(root);
+
+        while(!stack.isEmpty()) {
+            TreeNode cur = stack.pop();
+
+            TreeNode temp = cur.left;
+            cur.left = cur.right;
+            cur.right = temp;
+
+            if (cur.left != null) stack.push(cur.left);
+
+            if (cur.right != null) stack.push(cur.right);
+        }
+        return root;
+    }
+}