2. reorder-list

Author: Sunjae95

reorder-list/sunjae95.js

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+/**
+ * @description
+ * 인덱스로 접근하지 못하는 구조를 인덱스로 접근하게 하여 two pointer로 풀이
+ *
+ * n = total node count
+ * time complexity: O(n)
+ * space complexity: O(n)
+ */
+var reorderList = function (head) {
+  // convert from queue to list
+  let travelNode = head;
+  const list = [];
+  while (travelNode) {
+    list.push(travelNode);
+    travelNode = travelNode.next;
+  }
+  // two pointer
+  let [left, right] = [0, list.length - 1];
+  const node = new ListNode();
+  let tail = node;
+
+  while (left <= right) {
+    // 1. left append
+    const leftNode = list[left];
+    leftNode.next = null;
+    tail.next = leftNode;
+    tail = leftNode;
+    // 2. conditional right append
+    const rightNode = list[right];
+    rightNode.next = null;
+    if (left !== right) {
+      tail.next = rightNode;
+      tail = rightNode;
+    }
+
+    left++;
+    right--;
+  }
+
+  head = node.next;
+};