單鏈表插入的幾種情況

鏈表插入

根據給定插入條件，可以分爲多種插入函數；

1. 給定插入位置pos 初始有0 1 兩種情況
2. 給定插入元素key 初始有前插和後插兩種情況

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#define N 100
#define OVERFLOW 0
#define OK 1

// list insert

typedef struct student
{
    int num;
    struct student *next;
}stu,*slist;

struct Node *creat(int n)
{
    int i;
    struct student *head, *p1, *p1_last;
    int a;
    head = NULL;
    printf("input the integers:\n");
    for(i=0; i<n; i++)
    {
        p1 = (slist)malloc(sizeof(stu)); //storage allocation
        scanf("%d",&a);
        p1->num = a;
        if(head == NULL)
        {
            head = p1;
            p1_last = p1;
        }
        else
        {
            p1_last->next = p1;
            p1_last = p1;
        }
    }
    p1_last->next = NULL;
    return head;
};


struct student *list_insert_posfst1(struct student* p, int val, int i)
{
    struct student *q = (slist)malloc(sizeof(stu));
    struct student *h = p;
    q->num = val;
    if(i == 1)  //every output is the case of i = 1; so i need to check whether if is constant right ;
    {
        q->next = p;
        return q;
    }
    else
    {
        i-=2;
        while(i--)
        {
            p = p->next;  //find insert front pointer;
            if(p == NULL)
                exit(1);
        }
        q->next = p->next;  //insert code
        p->next = q;
        return  h;
    }
};

struct student *list_insert_posfst0(struct student* p, int val, int i)
{
    struct student *q = (slist)malloc(sizeof(stu));
    struct student *h = p;
    q->num = val;
    if(i == 0)  //every output is the case of i = 1; so i need to check whether if is constant right ;
    {
        q->next = p;
        return q;
    }
    else
    {
        i--;
        while(i--)
        {
            p = p->next;  //find insert front pointer;
            if(p == NULL)
                exit(1);
        }
        q->next = p->next;  //insert code
        p->next = q;
        return  h;
    }
};

struct student *list_insert_afterkey(struct student* p, int val, int key)
{
    slist h = p;
    slist q = (slist)malloc(sizeof(stu));
    q->num = val;
    while(p->num != key)
    {
        if(p == NULL) exit(1);
        p = p->next;
    }
    q->next = p->next;
    p->next = q;
    return h;
};

struct student *list_insert_beforekey(struct student* p, int val, int key)
{
    slist h = p;
    slist q = (slist)malloc(sizeof(stu));
    q->num = val;
    while(p->next->num != key)
    {
        if(p == NULL) exit(1);
        p = p->next;
    }
    q->next = p->next;
    p->next = q;
    return h;
};

int main()
{
    int temp,i,n;
    struct student*p, *head;
    printf("input the count of the list:\n");
    scanf("%d", &n);
    p = creat(n);
    head = list_insert_posfst0(p,521,3);
    printf("the position from 0 insert 521 :");
    while(head != NULL)
    {
        printf("%d ", head->num);
        head = head->next;
    }
    printf("\n\n");

    head = list_insert_posfst1(p,777,3);
    printf("the position from 1 insert 777 :");
    while(head != NULL)
    {
        printf("%d ", head->num);
        head = head->next;
    }
    printf("\n\n");

    head = list_insert_beforekey(p,999,3);
    printf("before 3 insert 999 :");
    while(head != NULL)
    {
        printf("%d ", head->num);
        head = head->next;
    }
    printf("\n\n");

    head = list_insert_afterkey(p,888,3);
    printf("after 3 insert 888 :");
    while(head != NULL)
    {
        printf("%d ", head->num);
        head = head->next;
    }
    printf("\n\n");
    return 0;
}