Question

所以我写了这个未完成但正在运行的代码。我是一个非常新的编程，我认为我的逻辑是错误的（虽然代码运行正常），因为有太多的＆＃34; ifs和elses＆＃34;我想不出另一个工作逻辑，将数据插入到链表的任何位置，并输出数据+错误处理，如果位置无效我试图开发计算思维并且有些东西告诉我这段代码可以写得更好

#include <stdio.h>
#include <stdlib.h>

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

struct node* head = NULL;


void Insert(int c ,int e)
{
    int i;
    static int p = 1;
    struct node* temp = malloc(sizeof(struct node));
    temp -> data = c;
    temp -> next = NULL;
   struct node* temp1 = head;

    if (e > p+1)
    {
        printf("Invalid Position");
        return;
    }

   else if (head == NULL)
        {
        head = temp;
        return;
        }

    else if (e <= 1)
    {
        temp -> next = head;
        head = temp;
        return;
    }

    else if (e == 2)
    {
        if (temp1 -> next != NULL)
        {
            temp -> next = temp1 -> next;
            temp1 -> next = temp;

        }

        else
        {
            temp1 -> next = temp;

        }

    }

    else
    {
        for (i = 0;i<e-2;i++)
        {
            temp1 = temp1 -> next;
        }

    temp -> next = temp1 -> next;
    temp1 -> next = temp;
    }
p++;
}

void print() {

    struct node* temp = head;
    printf("list is: \n");
    while (temp != NULL) {

        printf( "%d ,",temp->data);
        temp = temp->next;
    }
}


int main () {

printf("How Many Numbers?\n");
int a ,b ,c, e;
scanf("%d" , &b);
for(a = 0;a<b;a++) {
    printf("Enter the numbers \n");
    scanf("%d",&c);
    printf("Enter position \n");
    scanf("%d",&e);
    Insert(c , e);
    print();
}
return 0;
}

Answer 1

是的，您可以通过将两个条件合并为一个来降低深度：

    if (e > p + 1) {
        printf("Invalid Position");
        return;
    }
    else if (head == NULL) {
        head = temp;
        return;
    }
    else if (e <= 1) {
        temp->next = head;
        head = temp;
        return;
    }
    else if (e == 2 && temp1->next != NULL) {
        temp->next = temp1->next;
        temp1->next = temp;

    }
    else if (temp1->next == NULL) {
        temp1->next = temp;

    }
    else {
        for (i = 0; i < e - 2; i++) {
            temp1 = temp1->next;
        }
        temp->next = temp1->next;
        temp1->next = temp;
    }

Answer 2

确定if和else是不是一个好的模式设计，但你应该在C中使用它。当你使用OOP（面向对象编程）语言时，你可以改变你的设计。

在C中你应该有一个模块化的代码，所以只需要用尽可能多的函数来编写代码的较小部分。

Answer 3

您的insert功能可以简化一点。基本上你需要考虑三个条件：

将第一个节点插入空列表;

插入新的第一个节点;和

在第一个和最后一个之间插入一个新节点。

最后插入是默认值，无需特别考虑。单独编码每个，您可以按如下方式重写insert：

void insert (int c, int e)
{
    struct node *temp = malloc (sizeof *temp);
    if (!temp) {
        fprintf (stderr, "error: virtual memory exhausted.\n");
        exit (EXIT_FAILURE);
    }

    temp->data = c;
    temp->next = NULL;

    if (!head) { head = temp; goto check; }  /* empty list */

    struct node *iter = head;

    if (!e) { temp->next = head; head = temp; return; } /* new 1st node */
    for (--e; e && iter->next; iter = iter->next, e--) {}    /* iterate */

    /* inserting before end, update temp->next */
    if (iter->next) temp->next = iter->next;
    iter->next = temp;     /* add node as next */

  check:;
    if (e)
        fprintf (stderr, "warning, 'e' beyond list, inserted at end.\n");
}

注意： insert代替Insert。 C避免Caps和caMelCase变量和函数名称支持所有小写。参见例如NASA - C Style Guide, 1994

如果要为列表分配内存，则应跟踪已分配的内存，以便在不再需要时释放内存。尽早养成良好的习惯，不要仅仅依靠退出为你做好准备。您已撰写print()，delete()几乎相同：

void delete ()
{
    struct node *tmp = head;
    while (tmp != NULL) {
        struct node *victim = tmp;
        tmp = tmp->next;
        free (victim);
    }
}

将所有部分组合在一起并稍微清理剩余的代码，您可以按如下方式重写示例：

#include <stdio.h>
#include <stdlib.h>

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

struct node *head = NULL;

void insert (int c, int e);
void print ();
void delete ();

int main (void) {

    int a, b, c, e, rtn;
    a = b = c = e = rtn = 0;

    printf ("\nDefine list, values and positons (zero based positions)\n\n");
    do {
        printf (" numer of list elements?: ");
        if ((rtn = scanf ("%d", &b)) != 1 || b < 1)
            fprintf (stderr, "error: invalid input.\n");
        if (rtn == EOF) exit (EXIT_FAILURE);
    } while (b < 1);

    for (a = 0; a < b; a++) {
        do printf ("\n  number %2d: ", a + 1);
        while ((rtn = scanf ("%d", &c)) != 1 && rtn != EOF);
        if (rtn == EOF) exit (EXIT_FAILURE);

        do printf ("  position : ");
        while ((rtn = scanf ("%d", &e)) != 1 && e >= 0 && rtn != EOF);
        if (rtn == EOF) exit (EXIT_FAILURE);

        insert (c, e);
        print ();
    }
    delete ();
    return 0;
}

void insert (int c, int e)
{
    struct node *temp = malloc (sizeof *temp);
    if (!temp) {
        fprintf (stderr, "error: virtual memory exhausted.\n");
        exit (EXIT_FAILURE);
    }

    temp->data = c;
    temp->next = NULL;

    if (!head) { head = temp; goto check; }  /* empty list */

    struct node *iter = head;

    if (!e) { temp->next = head; head = temp; return; } /* new 1st node */
    for (--e; e && iter->next; iter = iter->next, e--) {}    /* iterate */

    /* inserting before end, update temp->next */
    if (iter->next) temp->next = iter->next;
    iter->next = temp;     /* add node as next */

  check:;
    if (e)
        fprintf (stderr, "warning, 'e' beyond list, inserted at end.\n");
}

void print ()
{
    struct node *temp = head;
    printf (" current list is: ");
    while (temp != NULL) {
        printf (" %d", temp->data);
        temp = temp->next;
    }
    putchar ('\n');
}

void delete ()
{
    struct node *tmp = head;
    while (tmp != NULL) {
        struct node *victim = tmp;
        tmp = tmp->next;
        free (victim);
    }
}

示例使用/输出

$ ./bin/llins

Define list, values and positons (zero based positions)

 numer of list elements?: 5

  number  1: 6
  position : 0
 current list is:  6

  number  2: 7
  position : 3
warning, 'e' beyond list, inserted at end.
 current list is:  6 7

  number  3: 8
  position : 0
 current list is:  8 6 7

  number  4: 9
  position : 2
 current list is:  8 6 9 7

  number  5: 10
  position : 3
 current list is:  8 6 9 10 7

仔细看看，如果您有任何问题，请告诉我。

寻找不同的逻辑

3 个答案: