feat: 25. Reverse Nodes in k-Group : 链表

Author: upupming

leetcode/残酷刷题/25. Reverse Nodes in k-Group.js

@@ -0,0 +1,37 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @param {number} k
+ * @return {ListNode}
+ */
+const reverseKGroup = function (head, k) {
+  let sz = 0
+  let a = head
+  while (a) sz++, a = a.next
+
+  const dummy = new ListNode(0, head)
+  // x: dummy, y: 1
+  let x = dummy; let y = dummy.next
+  for (let i = 0; i < Math.floor(sz / k); i++) {
+    a = y
+    let b = a.next
+    // 节点个数为 k，只需要反转 k-1 次中间的边
+    for (let j = 0; j < k - 1; j++) {
+      const c = b.next
+      b.next = a
+      a = b, b = c
+    }
+    // dummy -> 2, 1 -> 3
+    x.next = a, y.next = b
+    // x: 1, y: 3
+    x = y, y = y.next
+  }
+
+  return dummy.next
+}

leetcode/残酷刷题/README.md

@@ -171,6 +171,7 @@
 
 - 206. Reverse Linked List
 - 92. Reverse Linked List II
+- 25. Reverse Nodes in k-Group
 
 ## Links