c實現單向鏈表

實現一個單向鏈表的：建立、插入、刪除、排序（冒泡）、逆向、搜索中間節點 

  

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;

typedef struct student
{
    int data;
    struct student *next;
} node;

//建立鏈表
node *create()
{
    //1. 定義變量
    node *head = NULL;
    node *p = NULL;
    node *pnew = NULL;

    int x = 0;
    int cycle = 1;

    //2. 新建頭節點
    head = (node*)malloc(sizeof(node));
    p = head;

    //3. 添加新節點
    while (cycle)
    {
        printf("input data:");
        scanf("%d", &x);
      if (x != 0)    
        {
            pnew = (node*)malloc(sizeof(node));
            pnew->data = x;
            p->next = pnew;
            p = pnew;
        }
        else
        {
            cycle = 0;
        }
    }

    //4. 釋放頭節點
    p->next = NULL;
    p = head;
    head = head->next;
    free(p);
    p = NULL;
    
    //5. 返回鏈表
    return head;
}

//計算鏈表長度
int length(node *head)
{
    //1. 定義變量
    node *p = NULL;
    int n = 0;

    //2. 遍歷累加
    p = head;        
    while (p != NULL)
    {
        p = p->next;
        n++;
    }
    printf("%d\n", n);
    
    //3. 返回計數
    return n;
}

//顯示
void show(node *head)
{
    //1. 定義變量
    node *p = NULL;

    //2. 遍歷打印
    p = head;
 
    while(p != NULL)
    {
        printf("data:%d ", p->data); 
        p = p->next;
    }
    printf("\n");

}



//插入節點（升序）
node *insert (node *head, int num)
{
    //1. 定義變量
    node *p0 = NULL;
    node *p1 = NULL;
    node *p2 = NULL;

    //2. 新建節點
    p0 = (node*)malloc(sizeof(node));
    p0->data = num;
    
    //3. 定位插入位置（升序）
    p1 = head;
    while (p0->data > p1->data && p1->next != NULL)
    {
        p2 = p1;
        p1 = p1->next;
    }

    //4. 插入節點
    if (p0->data > p1->data) //末尾
    {
        p1->next = p0;
        p0->next = NULL;
    }
    else
    {

        if (head == p1) //頭
        {
            p0->next = p1;
            head = p0;
        }
        else //中間
        {
            p2->next = p0;
            p0->next = p1;
        }
    }

    //5. 返回頭
    return head;
}

//刪除鏈表中指定節點
node *del(node *head, int num)
{
    //1. 定義變量
    node *p1 = NULL;
    node *p2 = NULL;

    //2. 定位刪除位置
    p1 = head;
    while (num != p1->data && p1->next != NULL)
    {
        p2 = p1;
        p1 = p1->next;
    }

    //3. 刪除節點
    if (num != p1->data)
    {
        printf("not found data to delete\n");
    }
    else
    {        
        if(p1 == head)
        {
            head = p1->next;
            free(p1);
            p1 = NULL;
        }
        else
        {
            p2->next = p1->next;
            free(p1);
            p1 = NULL;
        }
    }

    //4. 返回頭
    return head;

}

//鏈表升序排序（冒泡算法）
node *sort(node *head)
{
    //1. 定義變量 
    node *p = NULL;
    int n = 0;
    int temp = 0;


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

    //2. 獲取鏈表長度
    n = length(head);
    
    //3. 排序
    for (int j=1; j<n; ++j) //遍歷全部節點
    {
        p = head; 
        for(int i=0; i<n-j; ++i) //遍歷未排序好的節點
        {
            if (p->data > p->next->data)
            {
                temp = p->data;
                p->data = p->next->data;
                p->next->data = temp;
            }

            p = p->next;
        }
    }

    //4. 返回頭
    return head;

}

//鏈表逆置
node *reverse(node *head)
{
    //1. 定義變量 
    node *p1 = NULL;
    node *p2 = NULL;
    node *p3 = NULL;
    
    if (head == NULL || head->next == NULL)
    {
        return head;
    }

    //2. 逆置
    p1 = head;
    p2 = p1->next;
    while(p2 != NULL)
    {
        p3 = p2->next;
        p2->next = p1;
        p1 = p2;
        p2 = p3;
    }

    //3. 調換頭尾節點
    head->next = NULL; //轉置完後頭節點成爲尾節點
    head = p1;         //轉置完後尾節點成爲頭節點

    //4. 返回頭
    return head;

}

//搜索鏈表中間節點
//算法：以步長2和1單位同時遍歷鏈表，步長2到末尾，步長1到中間
void searchmid(node *head, node *mid)
{
    //1. 定義變量
    node *p1 = NULL;
    node *p2 = NULL;
    
    //2. 定位中間節點
    p1 = head;
    p2 = head;
    while (p2->next != NULL && p2->next->next != NULL)
    {
        p1 = p1->next;
        mid = p1;
        p2 = p2->next->next;
    }

    printf("mid:%d\n", mid->data);
}

int main()
{
    node *head = create();
    int len = length(head);
    show(head);

    head = insert(head, 2);
    show(head);

    head = del(head, 2);
    show(head);

    head = sort(head);
    show(head);
    
    head = reverse(head);
    show(head);

    node *mid;
    searchmid(head, mid);
}