add: K个一组翻转链表

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

@@ -0,0 +1,49 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @param {number} k
+ * @return {ListNode}
+ */
+export const reverseKGroup = function (head, k) {
+  let sum = 0
+  let start = head
+  let newStart = head
+  let first = true
+  const last = []
+  while (head) {
+    if (++sum === k) {
+      const headNext = head.next
+      last.push(start)
+      let next = head.next
+      for (let i = 0; i < sum - 1; i++) {
+        const tmp = start.next
+        start.next = next
+        next = start
+        start = tmp
+      }
+
+      start.next = next
+
+      if (first) {
+        newStart = start
+        first = false
+      } else {
+        const la = last.shift()
+        la.next = head
+      }
+      sum = 0
+      start = headNext
+      head = headNext
+    } else {
+      head = head.next
+    }
+  }
+
+  return newStart
+}