[小算法] 交换链表中的两个节点

算法代码：

// SwitchLinkNodes.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "iostream"
#include "fstream"

using namespace std;
ifstream fin("data.txt");

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

void SwitchLinkNodes(Link *head, Link *nodeA, Link *nodeB);
Link* BuildLink();
void PrintLink(Link *head);
Link* GetNodeAtIndex(Link *head,int index);

int _tmain(int argc, _TCHAR* argv[])
{
    Link *head = BuildLink();
    PrintLink(head);
    cout << endl;
    Link *nodeA = GetNodeAtIndex(head, 3);
    Link *nodeB = GetNodeAtIndex(head, 5);

    SwitchLinkNodes(head, nodeA, nodeB);
    PrintLink(head);
    cout << endl;
    system("pause");
    return 0;
}

void SwitchLinkNodes(Link *head, Link *nodeA, Link *nodeB)
{
    if(nodeA == NULL || nodeB == NULL || head == NULL || head->Next == NULL)
        return;
    Link *nodeAPre, *nodeBPre, *pointer;
    pointer = head;
    //Get the previous nodes which will switch
    while(pointer)
    {
        if(pointer->Next == nodeA)
        {
            nodeAPre = pointer;
        }
        if(pointer->Next == nodeB)
        {
            nodeBPre = pointer;
        }
        pointer = pointer->Next;
    }

    nodeAPre->Next = nodeB;        //1
    nodeBPre->Next = nodeA;        //2
    pointer = nodeB->Next;        // 3.temp node
    nodeB->Next = nodeA->Next;    //4
    nodeA->Next = pointer;        //5
}

//Build link with the data in file data.txt
Link* BuildLink()
{
    Link * head = new Link();
    int data = -1;
    Link *newNode, *pointer;
    pointer = head;
    while(fin >> data)
    {
        newNode = new Link();
        newNode->Data = data;
        newNode ->Next = NULL;
        pointer->Next = newNode;
        pointer = newNode;
    }
    return head;
}

void PrintLink(Link *head)
{
    Link *pointer = head->Next;
    while(pointer != NULL)
    {
        cout << pointer->Data << " ";
        pointer = pointer->Next;
    }
}

//zero based index
Link* GetNodeAtIndex(Link *head,int index)
{
    int i = 0;
    Link *pointer = head->Next;
    for(i = 0;i < index;i++)
    {
        if(pointer != NULL)
        {
            pointer = pointer->Next;
        }
        else
        {
            return NULL;
        }
    }
    return pointer;
}

 

data.txt 文件内容如下：

2 3 6 8 9 12 7 45 56 66 4

 

程序运行结果：

2 3 6 8 9 12 7 45 56 66 4
2 3 6 12 9 8 7 45 56 66 4
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