feat: Add solution for LeetCode problem 105

Author: WhiteHyun

construct-binary-tree-from-preorder-and-inorder-traversal/WhiteHyun.swift

@@ -0,0 +1,47 @@
+//  
+//  105. Construct Binary Tree from Preorder and Inorder Traversal
+//  https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/
+//  Dale-Study
+//  
+//  Created by WhiteHyun on 2024/06/27.
+//  
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+  func buildTree(_ preorder: [Int], _ inorder: [Int]) -> TreeNode? {
+    let indices: [Int: Int] = Dictionary(uniqueKeysWithValues: inorder.enumerated().map { ($0.element, $0.offset) })
+
+    var preorderIndex = 0
+
+    func build(_ left: Int, _ right: Int) -> TreeNode? {
+      if left > right { return nil }
+
+      let rootValue = preorder[preorderIndex]
+      preorderIndex += 1
+      let root = TreeNode(rootValue)
+
+      let mid = indices[rootValue]!
+
+      root.left = build(left, mid - 1)
+      root.right = build(mid + 1, right)
+
+      return root
+    }
+
+    return build(0, inorder.count - 1)
+  }
+}