我的第一本算法书——链表的C语言实现

说明

改代码实现了链表的可选择初始化，链表结点的插入和删除，对于无效删除做出了处理。

代码片段

#include 
#include 

typedef struct list
{
    int x;
    struct list *next;
} T;
T *head = NULL;
T *pre = NULL;
T *cur = NULL;
void bianlilist(void); 
void deletelist(void); 
void addlist(void);    
int freal(void);
int main()
{
    puts("Please enter a number, i will build a list from 0 to the number, if you don't need, you can enter the number 0.");
    int n;
    scanf("%d", &n);
    getchar();
    
    for (int i = 0; i < n; i++)
    {
        cur = (T *)malloc(sizeof(T));
        cur->next = NULL;
        if (head == NULL)
            head = cur;
        else
            pre->next = cur;
        cur->x = i;
        pre = cur;
    }
    while (1)
    {
        int c = freal();
        if (c)
            break;
    }
    while (getchar() != 'n')
        ;
    return 0;
}
void bianlilist(void) 
{
    T *ps = head;
    int flag = 0;
    while (ps != NULL)
    {
        if (flag == 0)
        {
            printf("%d", ps->x);
            flag++;
        }
        else
            printf(" - %d", ps->x);
        ps = ps->next;
    }
    putchar('n');
}
void deletelist(void) 
{

    printf("nPlease enter the number which you want to delete: ");
    int y;
    scanf("%d", &y);
    getchar();
    T *ps = head;
    T *temp;
    if (head->x == y)
    {
        temp = head;
        head = head->next;
        free(temp);
        return;
    }
    int flag=0;
    while (1)
        {
            if(ps->next==NULL)
            {
                puts("Invalid input! Please enter again!");
                return;
            }
            if(ps->next->x != y)
            ps = ps->next;
            else
            break;
        }
    temp = ps->next;
    ps->next = temp->next;
    free(temp);
}
void addlist(void) 
{
    int y;
    printf("nPlease enter the number which you want to add: ");
    scanf("%d", &y);
    getchar();
    T *ps = head;
    T *temp = (T *)malloc(sizeof(T));
    temp->x = y;
    temp->next=NULL;
    if (head == NULL)
    {
        head = temp;
        return;
    }
    if (y < head->x)
    {
        temp->next = head;
        head = temp;
        return;
    }
    while (1)
    {

        if (ps->next == NULL)
        {
            ps->next = temp;
            return;
        }
        if (ps->next->x >= y)
            break;
        else
            ps = ps->next;
    }
    temp->next = ps->next;
    ps->next = temp;
}
int freal(void)
{
    printf("What function do you want to realize?n");
    puts("a.Add a element.  b.Delete a element");
    puts("c.Output the list.    d.Quit program.");
    char ch = getchar();
    getchar();
    switch (ch)
    {
    case 'a':
        addlist();
        break;
    case 'b':
        deletelist();
        break;
    case 'c':
        bianlilist();
        break;
    case 'd':
        return 1;
    default:
        puts("Invalid input! Please enter again!");
    }
    return 0;
}