[小算法] 反转单链表

#include "stdafx.h"
#include <iostream>
using namespace std;

struct Link
{
    int Data;
    Link *Next;
};

void PrintLink(Link *head);
void PrintReverse(Link *node);
Link ReverseLink(Link *head);
Link RecurseReverseLink(Link *head);
int PrintReverseAt(Link *node, int lastIndex);

int _tmain(int argc, _TCHAR* argv[])
{
    struct Link head, node1,node2,node3,node4;
    head.Data = 0;
    head.Next = &node1;
    node1.Data = 1;
    node1.Next = &node2;
    node2.Data = 2;
    node2.Next = &node3;
    node3.Data = 3;
    node3.Next = &node4;
    node4.Data = 4;
    node4.Next = NULL;

    PrintLink(&head);
    cout << endl;

    PrintReverseAt(&head, 3);
    cout << endl;

    PrintReverse(head.Next);
    cout << endl;

    ReverseLink(&head);
    PrintLink(&head);
    cout << endl;
    cin.get();
    return 0;
}

void PrintLink(Link *head)
{
    if(head == NULL) return;

    Link *node = head->Next;
    while(node)
    {
        cout << node->Data << " ";
        node = node->Next;
    }
}

//倒序打印链表
void PrintReverse(Link *node)
{
    if(node->Next != NULL)
    {
        PrintReverse(node->Next);
    }
    cout << node->Data << " ";
}

//输出链表中倒数第N个数
int PrintReverseAt(Link *node, int lastIndex)
{
    if(node->Next != NULL)
    {
        int currentLastIndex = PrintReverseAt(node->Next, lastIndex) + 1;
        if(currentLastIndex == lastIndex)
        {
            cout << node->Data;
        }
        return currentLastIndex;
    }
    if(lastIndex == 0)
    {
        cout << node->Data;
    }
    return 0;
}

Link ReverseLink(Link *head)
{
    if(head == NULL || head->Next == NULL || head->Next->Next == NULL) return *head;

    Link *current = head->Next;
    Link * next = head->Next->Next;
    Link * nnext = head->Next->Next->Next;
    
    current->Next = NULL;

    while(next != NULL)
    {
        nnext = next->Next;
        head->Next = next;
        next->Next = current;
        current = next;
        next = nnext;
    }

    return *head;
}