feat: Add solution for LeetCode problem 143

Author: WhiteHyun

reorder-list/WhiteHyun.swift

@@ -0,0 +1,43 @@
+//  
+//  143. Reorder List
+//  https://leetcode.com/problems/reorder-list/description/
+//  Dale-Study
+//  
+//  Created by WhiteHyun on 2024/06/10.
+//  
+
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init() { self.val = 0; self.next = nil; }
+ *     public init(_ val: Int) { self.val = val; self.next = nil; }
+ *     public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
+ * }
+ */
+class Solution {
+  func reorderList(_ head: ListNode?) {
+    guard head?.next != nil else { return }
+
+    var nodeList: [ListNode] = []
+    var tempNode = head
+
+    // 1. 각 노드를 선형으로 확인하며 리스트에 추가
+    while let node = tempNode {
+      nodeList.append(node)
+      tempNode = node.next
+    }
+
+    // 2. 각각 next 설정을 snail하게 만듦
+    for index in 0 ..< nodeList.count >> 1 {
+      nodeList[nodeList.count - index - 1].next = nodeList[index].next === nodeList[nodeList.count - index - 1] ? nil : nodeList[index].next
+      nodeList[index].next = nodeList[nodeList.count - index - 1]
+    }
+
+    //　추가. 만약 노드가 홀수라면 가운데 노드의 next를 nil로 설정
+    if nodeList.count & 1 == 1 {
+      nodeList[nodeList.count >> 1].next = nil
+    }
+  }
+}