[Week2](gmlwls96) construct binary tree from preorder and inorder traversal

Author: gmlwls96

construct-binary-tree-from-preorder-and-inorder-traversal/gmlwls96.kt

@@ -0,0 +1,25 @@
+class Solution {
+    // 시간 : O(n^2)
+    fun buildTree(preorder: IntArray, inorder: IntArray): TreeNode? {
+        if (preorder.isEmpty() || inorder.isEmpty()) {
+            return null
+        }
+        val value = preorder[0]
+        var mid = inorder.indexOf(value)
+        if (mid < 0) {
+            mid = 0
+        }
+        val leftNode = buildTree(
+            preorder.slice(1..preorder.lastIndex).toIntArray(),
+            inorder.slice(0 until mid).toIntArray())
+        val rightNode = buildTree(
+            preorder.slice(2..preorder.lastIndex).toIntArray(),
+            inorder.slice(mid + 1..inorder.lastIndex).toIntArray()
+        )
+
+        return TreeNode(value).apply {
+            left = leftNode
+            right = rightNode
+        }
+    }
+}