[leet] bst

Author: hyeonbinHur

허현빈/11주차/Construct Binary Tree from Preorder and Inorder Traversal.js

@@ -0,0 +1,38 @@
+/**
+ * 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) {
+  const map = new Map();
+
+  for (let i = 0; i < inorder.length; i++) {
+    map.set(inorder[i], i);
+  }
+
+  let preIdx = 0;
+
+  const build = (left, right) => {
+    if (left > right) return null;
+
+    const rootVal = preorder[preIdx++];
+    const root = new TreeNode(rootVal);
+
+    const mid = map.get(rootVal);
+
+    root.left = build(left, mid - 1);
+    root.right = build(mid + 1, right);
+
+    return root;
+  };
+
+  return build(0, inorder.length - 1);
+};