Add file reverse-linked-list-ii.go

Author: tinycedar

reverse-linked-list-ii.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"bytes"
+)
+
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func (n *ListNode) String() string {
+	var buf bytes.Buffer
+	for nn := n; nn != nil; nn = nn.Next {
+		buf.WriteString(fmt.Sprintf("[%d]", nn.Val))
+	}
+	return buf.String()
+}
+
+func reverseBetween(head *ListNode, m int, n int) *ListNode {
+	if head == nil || head.Next == nil || m <= 0 || n <= 0 || m >= n {
+		return head
+	}
+	mNode, nNode := findSubList(head, m, n)
+	if mNode == nil || nNode == nil || mNode == nNode {
+		return head
+	}
+	nextSubNode := nNode.Next
+	h, t := doReverse(mNode, nNode)
+	t.Next = nextSubNode
+	if t == head {
+		return h
+	}
+
+	for n := head; n != nil; n = n.Next {
+		if n.Next == t {
+			n.Next = h
+			break
+		}
+	}
+	return head
+}
+
+func doReverse(head, tail *ListNode) (*ListNode, *ListNode) {
+	if head == nil || tail == nil || head == tail {
+		return tail, head
+	}
+	pre, cur, next := head, head.Next, head.Next.Next
+	for {
+		cur.Next = pre
+		if cur == tail {
+			break
+		}
+		pre = cur
+		cur = next
+		next = next.Next
+	}
+	head.Next = nil
+	return tail, head
+}
+
+func findSubList(head *ListNode, m, n int) (mNode, nNode *ListNode) {
+	if head == nil {
+		return nil, nil
+	}
+	mNode, nNode = head, head
+	for i := 1; i < n; i++ {
+		if i < m {
+			mNode = mNode.Next
+			if mNode == nil {
+				return
+			}
+		}
+		nNode = nNode.Next
+		if nNode == nil {
+			return
+		}
+	}
+	return
+}
+
+func main() {
+	h := &ListNode{1, &ListNode{2, &ListNode{3, &ListNode{4, &ListNode{5, nil}}}}}
+	//h := &ListNode{3, &ListNode{5, nil}}
+	fmt.Println(h)
+	fmt.Println(reverseBetween(h, 3, 4))
+}