add Construct Binary Tree From Preorder And Inorder Traversal solution

Author: HoonDongKang

construct-binary-tree-from-preorder-and-inorder-traversal/HoonDongKang.ts

@@ -0,0 +1,41 @@
+/**
+ * [Problem]: [105] Construct Binary Tree From Preorder And Inorder Traversal
+ * (https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/)
+ */
+
+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;
+    }
+}
+
+//시간복잡도 O(n)
+//공간복잡도 O(n)
+function buildTree(preorder: number[], inorder: number[]): TreeNode | null {
+    if (!preorder.length || !inorder.length) return null;
+
+    const map = new Map<number, number>();
+    let idx = 0;
+
+    inorder.forEach((v, i) => map.set(v, i));
+
+    function dfs(left: number, right: number): TreeNode | null {
+        if (left > right) return null;
+
+        const value = preorder[idx++];
+        const root = new TreeNode(value);
+        const index = map.get(value)!;
+
+        root.left = dfs(left, index - 1);
+        root.right = dfs(index + 1, right);
+
+        return root;
+    }
+
+    return dfs(0, inorder.length - 1);
+}