reverse_nodes_in_k_group

Author: hitzzc

Diff for: README.md

@@ -25,5 +25,6 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [22. generate parentheses](https://github.com/hitzzc/go-leetcode/tree/master/generate_parentheses)
 #### [23. merge k sorted lists](https://github.com/hitzzc/go-leetcode/tree/master/merge_k_sorted_lists)
 #### [24. swap nodes in pairs](https://github.com/hitzzc/go-leetcode/tree/master/swap_nodes_in_pairs)
+#### [25. reverse nodes in k group](https://github.com/hitzzc/go-leetcode/tree/master/reverse_nodes_in_k_group)
 
 

Diff for: reverse_nodes_in_k_group/reverse_nodes_in_k_group.go

@@ -0,0 +1,41 @@
+package reverse_nodes_in_k_group
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func reverseKGroup(head *ListNode, k int) *ListNode {
+	if k <= 0 {
+		return head
+	}
+	fake := &ListNode{Next: head}
+	p := fake
+	for p != nil {
+		p.Next = reverseKNodes(p.Next, k)
+		for i := 0; p != nil && i < k; i++ {
+			p = p.Next
+		}
+	}
+	return fake.Next
+}
+
+func reverseKNodes(head *ListNode, k int) *ListNode {
+	end := head
+	for k > 0 && end != nil {
+		end = end.Next
+		k--
+	}
+	if k > 0 {
+		return head
+	}
+	ret, pNode := end, head
+	var qNode *ListNode
+	for pNode != end {
+		qNode = pNode.Next
+		pNode.Next = ret
+		ret = pNode
+		pNode = qNode
+	}
+	return ret
+}

Diff for: reverse_nodes_in_k_group/reverse_nodes_in_k_group_test.go

@@ -0,0 +1,18 @@
+package reverse_nodes_in_k_group
+
+import (
+	"testing"
+)
+
+func TestReverseKGroup(t *testing.T) {
+	head := &ListNode{
+		Val: 1,
+		Next: &ListNode{
+			Val: 2,
+			Next: &ListNode{
+				Val: 3,
+			},
+		},
+	}
+	reverseKGroup(head, 2)
+}