[gitsunmin] Week 10 Solutions

invert-binary-tree/gitsunmin.ts

@@ -0,0 +1,34 @@
+/**
+ * https://leetcode.com/problems/invert-binary-tree/
+ * time complexity : O(n)
+ * space complexity : O(log N)
+ */
+
+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)
+    }
+}
+
+export const dfs = (root: TreeNode | null, inverted: TreeNode | null): TreeNode | null => {
+    if (!root) return null;
+
+    const left = dfs(root.left, inverted);
+    const right = dfs(root.right, inverted);
+
+    root.left = right;
+    root.right = left;
+
+    return root;
+};
+
+function invertTree(root: TreeNode | null): TreeNode | null {
+    if (!root) return null;
+
+    return dfs(root, new TreeNode(0));
+};