Merge remote-tracking branch 'origin/master'

Author: konstantin

src/easy/234. Palindrome Linked List .kt

@@ -1,5 +1,8 @@
 package easy
 
+import LinkedListTopic
+import StackTopic
+import TwoPointersTopic
 import utils.ListNode
 
 /**
@@ -9,18 +12,18 @@ import utils.ListNode
  * Given the head of a singly linked list, return true if it is a palindrome.
  */
 
-class Easy234 {
+class Easy234 : LinkedListTopic, TwoPointersTopic, StackTopic {
 
     fun isPalindrome(head: ListNode?): Boolean {
         if (head == null) return true
-        val resultList = ArrayList<Int>()
-        var currentNode = head
-        while (currentNode != null) {
-            resultList.add(currentNode.`val`)
-            currentNode = currentNode.next
+        val list = ArrayList<Int>()
+        var node = head
+        while (node != null) {
+            list.add(node.`val`)
+            node = node.next
         }
-        for (i in 0..resultList.size / 2) {
-            if (resultList[i] != resultList[resultList.size - 1 - i]) {
+        for (i in 0..list.size / 2) {
+            if (list[i] != list[list.size - 1 - i]) {
                 return false
             }
         }

src/medium/61. Rotate List .kt

@@ -0,0 +1,32 @@
+package medium
+
+import LinkedListTopic
+import TwoPointersTopic
+import utils.ListNode
+
+/**
+ * 61. Rotate List
+ * https://leetcode.com/problems/rotate-list/
+ *
+Given the head of a linked list, rotate the list to the right by k places.
+ */
+
+class Medium61 : LinkedListTopic, TwoPointersTopic {
+
+    fun rotateRight(head: ListNode?, k: Int): ListNode? {
+        val list = ArrayList<ListNode>()
+        var node = head
+        while (node != null) {
+            list.add(node)
+            node = node.next
+        }
+        val sentinel = ListNode(0)
+        node = sentinel
+        for (i in list.indices) {
+            node?.next = list[(i - (k % list.size) + list.size) % list.size]
+            node = node?.next
+        }
+        node?.next = null
+        return sentinel.next
+    }
+}