feat(solutions): add rotate_list

Author: WindomZ

README.md

@@ -24,6 +24,7 @@
 
 | # | Problem | Solution | Difficulty | Single Repetition Duration | LeetCode Run Time |
 | ---: | :----- | :--------: | :----------: | ----------: | ----------: |
+|61|[Rotate List][Solutions-61]|[WindomZ][Solutions-61-Go]|Medium|[34.0 ns/op/2 test cases][Solutions-61-Test]|? ms|
 |59|[Spiral Matrix II][Solutions-59]|[WindomZ][Solutions-59-Go]|Medium|[90.3 ns/op/3 test cases][Solutions-59-Test]|? ms|
 |58|[Length of Last Word][Solutions-58]|[WindomZ][Solutions-58-Go]|Easy|[4.02 ns/op/5 test cases][Solutions-58-Test]|0 ms|
 |56|[Merge Intervals][Solutions-56]|[WindomZ][Solutions-56-Go]|Medium|[154 ns/op/5 test cases][Solutions-56-Test]|19 ms|
@@ -113,6 +114,9 @@ Welcome to report bugs, suggest ideas and discuss on [issues page](https://githu
 ### Support
 If you like it then you can put a :star:Star on it.
 
+[Solutions-61-Test]:solutions/rotate_list/rotatelist_test.go#L29
+[Solutions-61-Go]:solutions/rotate_list/rotatelist.go
+[Solutions-61]:https://leetcode.com/rotate-list/
 [Solutions-59-Test]:solutions/spiral_matrix_ii/spiralmatrixii_test.go#L22
 [Solutions-59-Go]:solutions/spiral_matrix_ii/spiralmatrixii.go
 [Solutions-59]:https://leetcode.com/spiral-matrix-ii/

solutions/rotate_list/README.md

@@ -0,0 +1,11 @@
+# 61. Rotate List
+
+## Description
+
+Given a list, rotate the list to the right by _k_ places, where _k_ is non-negative.
+
+For example:  
+
+Given `1->2->3->4->5->NULL` and _k_ = `2`,  
+
+return `4->5->1->2->3->NULL`.

solutions/rotate_list/rotatelist.go

@@ -0,0 +1,33 @@
+package rotatelist
+
+// Definition for singly-linked list.
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func rotateRight(head *ListNode, k int) *ListNode {
+	if head == nil || k <= 0 {
+		return head
+	}
+
+	size := 1 // number of nodes
+	tail := head
+
+	// get the tail node
+	for ; tail.Next != nil; size++ {
+		tail = tail.Next
+	}
+	tail.Next = head // circle the nodes
+
+	if k %= size; k != 0 {
+		// the tail node is the (size-k)th node (1st node is head)
+		for i := 0; i < size-k; i++ {
+			tail = tail.Next
+		}
+	}
+
+	head = tail.Next
+	tail.Next = nil
+	return head
+}

solutions/rotate_list/rotatelist_test.go

@@ -0,0 +1,51 @@
+package rotatelist
+
+import (
+	"testing"
+
+	"github.com/WindomZ/testify/assert"
+)
+
+func Test_rotateRight(t *testing.T) {
+	var node *ListNode
+	assert.Equal(t, node, rotateRight(node, 0))
+
+	for i := 5; i >= 1; i-- {
+		node = &ListNode{
+			Val:  i,
+			Next: node,
+		}
+	}
+	node = rotateRight(node, 2)
+	val := []int{4, 5, 1, 2, 3}
+	for i := 0; i < 5; i++ {
+		if assert.NotEmpty(t, node) {
+			assert.Equal(t, val[i], node.Val)
+			node = node.Next
+		}
+	}
+}
+
+func Benchmark_rotateRight(b *testing.B) {
+	b.StopTimer()
+	b.ReportAllocs()
+
+	f := func() (node *ListNode) {
+		for i := 5; i >= 1; i-- {
+			node = &ListNode{
+				Val:  i,
+				Next: node,
+			}
+		}
+		return
+	}
+
+	b.StartTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			rotateRight(nil, 0)
+
+			rotateRight(f(), 2)
+		}
+	})
+}