92 accepted

Author: aQua

Algorithms/0092.reverse-linked-list-ii/README.md

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+# [92. Reverse Linked List II](https://leetcode.com/problems/reverse-linked-list-ii/)
+
+## 题目
+Reverse a linked list from position m to n. Do it in-place and in one-pass.
+
+```
+For example:
+Given 1->2->3->4->5->NULL, m = 2 and n = 4,
+return 1->4->3->2->5->NULL.
+```
+
+Note: Given m, n satisfy the following condition:
+1. 1 ≤ m ≤ n ≤ length of list.
+1. head 的序号为 1
+
+## 解题思路
+
+见程序注释

Algorithms/0092.reverse-linked-list-ii/reverse-linked-list-ii.go

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+package Problem0092
+
+// ListNode is Definition for singly-linked list.
+type ListNode struct {
+	Val  int
+	Next *ListNode
+}
+
+func reverseBetween(head *ListNode, m int, n int) *ListNode {
+	if m == n {
+		return head
+	}
+
+	// 添加 headPre 是为了 m >= 2
+	//
+	headPre := &ListNode{}
+	headPre.Next = head
+	m++
+	n++
+
+	mPre, mNode, nNext := split(headPre, m, n)
+
+	h, e := reverse(mNode)
+	mPre.Next = h
+	e.Next = nNext
+
+	return headPre.Next
+}
+
+func split(head *ListNode, m, n int) (mPre, mNode, nNext *ListNode) {
+	i := 1
+	for head != nil {
+		if i == m-1 {
+			mPre = head
+			mNode = head.Next
+		}
+		if i == n {
+			nNext = head.Next
+			head.Next = nil
+			break
+		}
+		head = head.Next
+		i++
+	}
+
+	return
+}
+
+func reverse(head *ListNode) (h, e *ListNode) {
+	if head == nil || head.Next == nil {
+		return head, head
+	}
+
+	var end *ListNode
+
+	h, end = reverse(head.Next)
+	end.Next = head
+	e = head
+
+	return
+}

Algorithms/0092.reverse-linked-list-ii/reverse-linked-list-ii_test.go

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+package Problem0092
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type question struct {
+	para
+	ans
+}
+
+// para 是参数
+type para struct {
+	head []int
+	m    int
+	n    int
+}
+
+// ans 是答案
+type ans struct {
+	one []int
+}
+
+func Test_Problem0092(t *testing.T) {
+	ast := assert.New(t)
+
+	qs := []question{
+
+		question{
+			para{
+				[]int{1, 2, 3, 4, 5},
+				2,
+				2,
+			},
+			ans{
+				[]int{1, 2, 3, 4, 5},
+			},
+		},
+
+		question{
+			para{
+				[]int{1, 2, 3, 4, 5},
+				2,
+				4,
+			},
+			ans{
+				[]int{1, 4, 3, 2, 5},
+			},
+		},
+
+		// 如需多个测试，可以复制上方元素。
+	}
+
+	for _, q := range qs {
+		a, p := q.ans, q.para
+		fmt.Printf("~~%v~~\n", p)
+
+		ast.Equal(a.one, l2s(reverseBetween(s2l(p.head), p.m, p.n)), "输入:%v", p)
+	}
+}
+
+// convert *ListNode to []int
+func l2s(head *ListNode) []int {
+	res := []int{}
+
+	for head != nil {
+		res = append(res, head.Val)
+		head = head.Next
+	}
+
+	return res
+}
+
+// convert []int to *ListNode
+func s2l(nums []int) *ListNode {
+	if len(nums) == 0 {
+		return nil
+	}
+
+	res := &ListNode{
+		Val: nums[0],
+	}
+	temp := res
+	for i := 1; i < len(nums); i++ {
+		temp.Next = &ListNode{
+			Val: nums[i],
+		}
+		temp = temp.Next
+	}
+
+	return res
+}