单链表的基本操作 C++

转载自https://blog.csdn.net/tianzhaixing2013/article/details/22786001
#include <iostream>
#include <stdio.h>
#include <string>
#include <conio.h>

/**
* cstdio是将stdio.h的内容用C++头文件的形式表示出来。
*stdio.h是C标准函数库中的头文件，即：standard buffered input&output。
*提供基本的文字的输入输出流操作（包括屏幕和文件等）。
*/

/**
*conio是Console Input/Output（控制台输入输出）的简写，其中定义了通过控制台进行数据输入和数据输出的函数，
*主要是一些用户通过按键盘产生的对应操作，比如getch()()函数等等。
*/

/**   查找链表的倒数第k个元素
*  为了实现只遍历链表一次就能找到倒数第k个节点，我们定义两个指针。
*  第一个指针从链表的头指针开始遍历向前走k-1步，第二个指针保持不动。
*  从第k步开始，第二个指针也开始从链表的头指针开始遍历。由于两个指针
*  的距离保持在k-1，当第一个指针到达链表的尾节点时，第二个指针刚好走到
*  倒数第k个节点。
*/

using namespace std;

struct node
{
    int data;  //链表的数据域
    node *next; //链表的指针域
};

// 创建单链表
node *creat()
{
    node *head, *p;  //head链表头结点
    head = new node;  //没有内存，何来指针
    p = head;

    int x, cycle = 1;  //x从键盘输入的数据 cycle算是标志位
    while (cycle)
    {
        cout << "Please input the data for single linker : ";
        cin >> x;   //2 4 5 0

        if (x != 0)
        {
            node *s = new node;
            s->data = x;  //s结点指向的数据域为键盘输入的x
            cout << "Input data : " << x << endl;

            p->next = s;
                //cout << p->data << endl;  //一串数字、 2、4
                //cout <<s->data << endl;  //2、4、5
            p = s;
                //cout << p->data << endl; //2、4、5
        }
        else
        {
            cycle = 0;
            cout << "Input done! " << endl;
        }
    } //返回while，判断while(cycle)，此时cycle为0，直接跳到head = head->next;

    //cout << head->data << endl; //一串数字
    head = head->next;
    //cout << head->data << endl;  //2 将head指向了下一个结点
    p->next = NULL;
    //cout << p->data << p->next << endl;  //5 00000000

    return head;
}

// 单链表测长
int length(node *head)
{
    int n = 0;
    node *p = head;

    while (p != NULL)
    {
        p = p->next;
        n++;
    }

    return n;
}

// 单链表打印 从头到尾
void PrintListFormHeadToTail(node *head)
{
    node *p = head;

    while (p != NULL)
    {
        cout << "Single Linker data is " << p->data << endl;
        p = p->next;
    }
}

// 单链表打印 从尾到头
void PrintListFormTailToHead(node *pHead)
{

    if (pHead == NULL)
    {
        return;
    }
    else
    {
        PrintListFormTailToHead(pHead->next);
        cout << "Single Linker data is " <<pHead->data << endl;
    }
}

// 单链表插入
node *insert(node *head, int num)
{
    node *p0, *p1, *p2;
    p1 = head;

    p2 = new node;
    p0 = new node; // 插入节点
    p0->data = num;// 插入数据

    while (p0->data > p1->data && p1->next != NULL)
    {
        p2 = p1;
        p1 = p1->next;// p0,p1和p2位置: p2->p1->p0
    }

    if (p0->data <= p1->data)
    {
        if (p1 == head)
        {// 头部前段插入 p0和p1位置: p0->p1->...
            head = p0;
            p0->next = p1;
        }
        else
        {// 插入中间节点 p0,p1和p2位置: p2-> p0 -> p1
            p2->next = p0;
            p0->next = p1;
        }
    }
    else
    {   // 尾部插入节点 p0,p1和p2位置: p2->p1->p0->NULL
        p1->next = p0;
        p0->next = NULL;
    }
    return head;
}

// 单链表删除
node *del(node *head, int num)
{
    node *p1, *p2;
    p2 = new node;
    p1 = head;

    while (num != p1->data && p1->next != NULL)
    {
        p2 = p1;
        p1 = p1->next;// p1和p2位置: p2->p1        
    }

    if (num == p1->data)
    {
        if (p1 == head)// 删除头节点
        {
            head = p1->next;
            delete p1;
        }
        else
        {
            p2->next = p1->next;
            delete p1;
        }
    }
    else
    {
        cout << num << " could not been found in the current single linker!" << endl;
    }
    return head;
}

// 单链表排序
node *sort(node *head)
{
    if (head == NULL || head->next == NULL)
    {
        return head;
    }

    node *p = head;// 初始化p指针为头结点

    int n, temp;
    n = length(head);

    for (int j = 0; j < n; j++)
    {
        p = head;
        for (int i = j + 1; i < n; i++)
        {
            if (p->data > p->next->data)
            {
                temp = p->data;
                p->data = p->next->data;
                p->next->data = temp;
            }
            else
            {
                p = p->next;
            }
        }
    }

    return head;
}

// 单链表逆置
node *reverse(node *head)
{
    node *p1, *p2, *p3;

    if (head == NULL || head->next == NULL)
    {
        return head;
    }

    p1 = head;
    p2 = head->next;

    while (p2)
    {
        p3 = p2->next;
        p2->next = p1;
        p1 = p2;
        p2 = p3;
    }

    head->next = NULL;
    head = p1;
    cout << head->data << endl;

    return head;
}

//单链表倒数第k个元素
node *findKthToTail(node *head, int k)
{
    node *fast = head;
    node *slow = NULL;
    if (head == NULL || k <= 0){
        return NULL;
    }
    for (int i = 0; i < k - 1; i++){
        fast = fast->next;
    }
    slow = head;
    while (fast->next != NULL){
        slow = slow->next;
        fast = fast->next;
    }
    cout << "The " << k << "th to tail is " << slow->data << endl;
    return slow;
}

//单链表的中间结点
node *SearchMid(node *head) //如果有两个中间结点，返回的是第一个
{
    node *slow = head;
    while (head->next != NULL && head->next->next != NULL)
    {
        head = head->next->next;
        slow = slow->next;
    }
    cout << "The mid is " << slow->data << endl;
    return slow;
}


int main()
{
    cout << "***创建单链表***" << endl;
    node *head = creat();
    cout << endl;

    cout << "***计算链表长***" << endl;
    int n = length(head);   //计算上一步创建的head链表的长度
    cout << "The length of input single linker is " << n << "." << endl;
    cout << endl;

    cout << "***打印单链表 从头到尾***" << endl;
    PrintListFormHeadToTail(head);  //从头到尾打印创建的head链表
    cout << endl;

    cout << "***打印单链表 从尾到头***" << endl;
    PrintListFormTailToHead(head);  //从尾到头打印创建的head链表
    cout << endl;

    cout << "****插入节点****" << endl;
    cout << "Please input the data for inserting operate : ";
    int inData;
    cin >> inData;
    head = insert(head, inData);   //在head链表中插入结点
    PrintListFormHeadToTail(head);
    cout << endl;

    cout << "****删除节点****" << endl;
    cout << "Please input the data for deleting operate : ";
    int outData;
    cin >> outData;
    head = del(head, outData);  //在head链表中删除结点
    PrintListFormHeadToTail(head);
    cout << endl;

    cout << "***单链表排序***" << endl;
    head = sort(head);   ////对head链表进行排序
    PrintListFormHeadToTail(head);
    cout << endl;

    //一层一层下来 head已经被改变了,此时是从小到大排序好的head

    cout << "***单链表逆置***" << endl;
    head = reverse(head);
    PrintListFormHeadToTail(head);   //将head链表逆置，但是逆置结果给了rev，此时不改变原来head链表的顺序
    cout << endl;


    cout << "***查找倒数第k个元素***" << endl;
    cout << "Please input the data for find Kth to tail : ";
    int findData;
    cin >> findData;
    node *Kth = findKthToTail(head, findData);    //在排序好的head链表中查找倒数第K个元素，结果返回给Kth
    cout << endl;


    cout << "***单链表的中间结点***" << endl;
    node *mid = SearchMid(head);     //在排序好的head链表中查找中间的结点，结果返回给mid
    cout << endl;

    return 0;
}