设计链表 没有Go单链表的实现只有循环双链表 添加单链表实现便于理解

problems/0707.设计链表.md

@@ -652,6 +652,106 @@ class MyLinkedList:
 
 Go：
 
+```go
+//单链表实现
+package main
+
+import "fmt"
+
+func main() {
+	var list = new(SingleLinkedList)
+	list.Init()
+	list.addAtHead(100)
+	list.addAtTail(242)
+	list.addAtTail(777)
+	list.addAtIndex(1, 99999)
+	list.printLinkedList()
+}
+
+// 单链表写法 //
+
+type SingleNode struct {
+	Val  int
+	Next *SingleNode
+}
+
+type SingleLinkedList struct {
+	dummyHead *SingleNode
+	Size      int
+}
+
+// 初始化链表
+func (list *SingleLinkedList) Init() *SingleLinkedList {
+	list.Size = 0
+	list.dummyHead = new(SingleNode)
+	return list
+}
+
+// 获取第index个节点数值
+func (list *SingleLinkedList) get(index int) int {
+	if list != nil || index < 0 || index > list.Size {
+		return -1
+	}
+	// 让cur等于真正头节点
+	cur := list.dummyHead.Next
+	for i := 0; i < index; i++ {
+		cur = cur.Next
+	}
+	return cur.Val
+}
+
+// 在链表最前面插入一个节点
+func (list *SingleLinkedList) addAtHead(val int) {
+	// 以下两行代码可用一行代替
+	// newNode := new(SingleNode)
+	// newNode.Val = val
+	newNode := &SingleNode{Val: val}
+
+	newNode.Next = list.dummyHead.Next
+	list.dummyHead.Next = newNode
+	list.Size++
+}
+
+// 在链表最后面插入一个节点
+func (list *SingleLinkedList) addAtTail(val int) {
+	newNode := &SingleNode{Val: val}
+	cur := list.dummyHead
+	for cur.Next != nil {
+		cur = cur.Next
+	}
+	cur.Next = newNode
+	list.Size++
+}
+
+// 打印链表
+func (list *SingleLinkedList) printLinkedList() {
+	cur := list.dummyHead
+	for cur.Next != nil {
+		fmt.Println(cur.Next.Val)
+		cur = cur.Next
+	}
+}
+
+// 在第index个节点之前插入新节点
+func (list *SingleLinkedList) addAtIndex(index int, val int) {
+	if index < 0 {
+		index = 0
+	} else if index > list.Size {
+		return
+	}
+
+	newNode := &SingleNode{Val: val}
+	cur := list.dummyHead //用虚拟头节点不用考虑在头部插入的情况
+	for i := 0; i < index; i++ {
+		cur = cur.Next
+	}
+	newNode.Next = cur.Next
+	cur.Next = newNode
+	list.Size++
+}
+
+```
+
 ```go
 //循环双链表
 type MyLinkedList struct {