add Invert Binary Tree solution

Author: HoonDongKang

invert-binary-tree/HoonDongKang.ts

@@ -0,0 +1,53 @@
+/**
+ * [Problem]: [226] Invert Binary Tree
+ * (https://leetcode.com/problems/invert-binary-tree/)
+ */
+
+class TreeNode {
+    val: number;
+    left: TreeNode | null;
+    right: TreeNode | null;
+    constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+        this.val = val === undefined ? 0 : val;
+        this.left = left === undefined ? null : left;
+        this.right = right === undefined ? null : right;
+    }
+}
+
+function invertTree(root: TreeNode | null): TreeNode | null {
+    // 시간복잡도 O(n)
+    // 공간복잡도 O(n)
+    function recursiveFunc(root: TreeNode | null): TreeNode | null {
+        if (root === null) {
+            return null;
+        }
+
+        const temp = root.left;
+        root.left = invertTree(root.right);
+        root.right = invertTree(temp);
+
+        return root;
+    }
+    // 시간복잡도 O(n)
+    // 공간복잡도 O(n)
+    function stackFunc(root: TreeNode | null): TreeNode | null {
+        if (root === null) {
+            return null;
+        }
+
+        const stack: Array<TreeNode | null> = [root];
+
+        while (stack.length > 0) {
+            const node = stack.pop()!;
+
+            if (node === null) {
+                continue;
+            }
+
+            [node.left, node.right] = [node.right, node.left];
+            stack.push(node.left, node.right);
+        }
+
+        return root;
+    }
+}