feat(每日一题): ✨考察链表基本操作

Author: descire

one-question-per-day/20201020/solution1.js

@@ -0,0 +1,52 @@
+const reorderList = head => {
+  if (!head || !head.next) {
+    return head;
+  }
+  
+  const half = findHalf(head);
+  const secondHalf = half.next;
+  half.next = null;
+
+  let newSecondHalf = reverseLinkedList(secondHalf);
+
+  // 合并
+  let currentHead = head;
+  while (currentHead && newSecondHalf) {
+    const x = currentHead.next;
+    const y = newSecondHalf.next;
+    currentHead.next = newSecondHalf;
+    newSecondHalf.next = x;
+    currentHead = x;
+    newSecondHalf = y;
+  }
+}
+
+// 寻找链表中间值
+function findHalf(head) {
+  let fast = head;
+  let slow = head;
+  while (fast && fast.next) {
+    fast = fast.next.next;
+    slow = slow.next;
+  }
+  
+  return slow;
+}
+
+// 翻转链表
+function reverseLinkedList(head) {
+  if (!head || !head.next) {
+    return head;
+  }
+
+  let nextNode = head.next;
+  head.next = null;
+  while (nextNode) {
+    const temp = nextNode.next;
+    nextNode.next = head;
+    head = nextNode;
+    nextNode = temp;
+  }
+
+  return head;
+}