package main

import "fmt"

type ListNode struct {
    next  *ListNode
    value interface{}
}

type LinkedList struct {
    head   *ListNode
    length uint
}

func NewListNode(v interface{}) *ListNode {
    return &ListNode{nil, v}
}

func (this *ListNode) GetNext() *ListNode {
    return this.next
 

}

func (this *ListNode) GetValue() interface{} {
    return this.value
}

func NewLinkedList() *LinkedList {
    return &LinkedList{NewListNode(0), 0}
}

//在某個節點後面插入節點
func (this *LinkedList) InsertAfter(p *ListNode, v interface{}) bool {
    if nil == p {
        return false
    }
    newNode := NewListNode(v)
    oldNext 
 
:= p.next
    p.next = newNode
    newNode.next = oldNext
    this.length++
    return true
}

//在某個節點前面插入節點
func (this *LinkedList) InsertBefore(p *ListNode, v interface{}) bool {
    if nil == p || p == this.head {
        return false
    }
    cur := this.head.next
    pre := this.head
    for nil != cur {
        
 
if cur == p {
            break
        }
        pre = cur
        cur = cur.next
    }
    if nil == cur {
        return false
    }
    newNode := NewListNode(v)
    pre.next = newNode
    newNode.next = cur
    this.length++
    return true
}

//在連結串列頭部插入節點
func (this *LinkedList) InsertToHead(v interface{}) bool {
    return this.InsertAfter(this.head, v)
}

//在連結串列尾部插入節點
func (this *LinkedList) InsertToTail(v interface{}) bool {
    cur := this.head
    for nil != cur.next {
        cur = cur.next
    }
    return this.InsertAfter(cur, v)
}

//通過索引查詢節點
func (this *LinkedList) FindByIndex(index uint) *ListNode {
    if index >= this.length {
        return nil
    }
    cur := this.head.next
    var i uint = 0
    for ; i < index; i++ {
        cur = cur.next
    }
    return cur
}

//刪除傳入的節點
func (this *LinkedList) DeleteNode(p *ListNode) bool {
    if nil == p {
        return false
    }
    cur := this.head.next
    pre := this.head
    for nil != cur {
        if cur == p {
            break
        }
        pre = cur
        cur = cur.next
    }
    if nil == cur {
        return false
    }
    pre.next = p.next
    p = nil
    this.length--
    return true
}

//列印連結串列
func (this *LinkedList) Print() {
    cur := this.head.next
    format := ""
    for nil != cur {
        format += fmt.Sprintf("%+v", cur.GetValue())
        cur = cur.next
        if nil != cur {
            format += "->"
        }
    }
    fmt.Println(format)
}

/*
單鏈表反轉
時間複雜度：O(N)
*/
func (this *LinkedList) Reverse() {
    if nil == this.head || nil == this.head.next || nil == this.head.next.next {
        return
    }

    var pre *ListNode = nil
    cur := this.head.next
    for nil != cur {
        tmp := cur.next
        cur.next = pre
        pre = cur
        cur = tmp
    }

    this.head.next = pre
}

/*
判斷單鏈表是否有環
*/
func (this *LinkedList) HasCycle() bool {
    if nil != this.head {
        slow := this.head
        fast := this.head
        for nil != fast && nil != fast.next {
            slow = slow.next
            fast = fast.next.next
            if slow == fast {
                return true
            }
        }
    }
    return false
}

/*
刪除倒數第N個節點
*/
func (this *LinkedList) DeleteBottomN(n int) {
    if n <= 0 || nil == this.head || nil == this.head.next {
        return
    }

    fast := this.head
    for i := 1; i <= n && fast != nil; i++ {
        fast = fast.next
    }

    if nil == fast {
        return
    }

    slow := this.head
    for nil != fast.next {
        slow = slow.next
        fast = fast.next
    }
    slow.next = slow.next.next
}

/*
獲取中間節點
*/
func (this *LinkedList) FindMiddleNode() *ListNode {
    if nil == this.head || nil == this.head.next {
        return nil
    }
    if nil == this.head.next.next {
        return this.head.next
    }

    slow, fast := this.head, this.head
    for nil != fast && nil != fast.next {
        slow = slow.next
        fast = fast.next.next
    }
    return slow
}

/*
兩個有序單鏈表合併
*/
func MergeSortedList(l1, l2 *LinkedList) *LinkedList {
    if nil == l1 || nil == l1.head || nil == l1.head.next {
        return l2
    }
    if nil == l2 || nil == l2.head || nil == l2.head.next {
        return l1
    }

    l := &LinkedList{head: &ListNode{}}
    cur := l.head
    curl1 := l1.head.next
    curl2 := l2.head.next
    for nil != curl1 && nil != curl2 {
        if curl1.value.(int) > curl2.value.(int) {
            cur.next = curl2
            curl2 = curl2.next
        } else {
            cur.next = curl1
            curl1 = curl1.next
        }
        cur = cur.next
    }

    if nil != curl1 {
        cur.next = curl1
    } else if nil != curl2 {
        cur.next = curl2
    }

    return l
}

/*
 * 遞迴實現 翻轉
 */
func (this *LinkedList) reve() bool {
    head := reverseList(this.head)
    p := head
    for true {
        if p == nil {
            break
        } else {
            if p.value == 0 {
                break
            }
            this.InsertToTail(p.value)
            p = p.next
        }
    }
    return true
}
func reverseList(node *ListNode) *ListNode {
    if node.next == nil {
        return node
    } else {
        newHead := reverseList(node.next)
        node.next.next = node
        node.next = nil
        return newHead
    }
}


func main() {
    list := NewLinkedList()
    list.InsertToTail(2)
    list.InsertToHead(1)
    list.InsertToTail(3)
    list.InsertToTail(4)

    list.Reverse()
    //list.reve()
    list.Print()
    if list.HasCycle() {
        fmt.Println("has cycle")
    }
}