update: K个一组翻转链表

src/list/reverse-nodes-in-k-group.js

@@ -11,33 +11,31 @@
  * @return {ListNode}
  */
 export const reverseKGroup = function (head, k) {
-  let sum = 0
+  let sum = 0 // 记录进行的结点个数
-  let start = head
+  let start = head // 记录每次翻转的第一个元素
-  let newStart = head
+  let res = head // 返回值：如果进行过翻转，则为第一次翻转的最后一个结点
-  let first = true
+  const queue = [] // 使用队列，方便连接上一次翻转的链表，最大长度为2
-  const last = []
+  while (head) { // 遍历一次链表
-  while (head) {
+    if (++sum === k) { // 如果经过了k个结点，则翻转从start到head的一段结点
-    if (++sum === k) {
       const headNext = head.next
-      last.push(start)
+      queue.push(start) // 计入队列
       let next = head.next
-      for (let i = 0; i < sum - 1; i++) {
+      for (let i = 0; i < sum - 1; i++) { // 翻转结点
         const tmp = start.next
         start.next = next
         next = start
         start = tmp
       }
 
-      start.next = next
+      start.next = next // 最后一个结点
 
-      if (first) {
+      if (queue.length === 1) { // 判断是否为第一次翻转
-        newStart = start
+        res = start
-        first = false
       } else {
-        const la = last.shift()
+        const la = queue.shift() // 连接上一次翻转的链表
         la.next = head
       }
-      sum = 0
+      sum = 0 // 重置计数
       start = headNext
       head = headNext
     } else {
@@ -45,5 +43,5 @@ export const reverseKGroup = function (head, k) {
     }
   }
 
-  return newStart
+  return res
 }