solve: construct binary tree from preorder and inorder traversal

Author: wogha95

construct-binary-tree-from-preorder-and-inorder-traversal/wogha95.js

@@ -0,0 +1,37 @@
+// TC: O(N) - leetcode analyze 기준
+// SC: O(N)
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {number[]} preorder
+ * @param {number[]} inorder
+ * @return {TreeNode}
+ */
+var buildTree = function (preorder, inorder) {
+  if (inorder.length === 0) {
+    return null;
+  }
+
+  if (inorder.length === 1) {
+    return new TreeNode(inorder[0]);
+  }
+
+  const rootValue = preorder[0];
+  const leftNodeLength = inorder.findIndex((value) => value === rootValue);
+  const leftNode = buildTree(
+    preorder.slice(1, 1 + leftNodeLength),
+    inorder.slice(0, leftNodeLength)
+  );
+  const rightNode = buildTree(
+    preorder.slice(1 + leftNodeLength),
+    inorder.slice(leftNodeLength + 1)
+  );
+  return new TreeNode(rootValue, leftNode, rightNode);
+};