Question

我有下一个代码，首先我从一个名为hc12的文件中创建一个列表，然后我搜索必须在列表中找到的codop =“BLE”，但我不断收到消息COULDNT FIND CODOP。我不知道为什么，链表运作良好。

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

typedef struct nodo
{
    char *code;
    struct nodo *next;
}COD;

COD *createNodo(char *instruction);
void insertEnd(char *instruction,COD *last);
COD *lastElement(COD *head);
void remove(char *c);
void searchEndofLine(FILE *fd);
void ignoreSpaces(FILE *fd);
void CodopsList(COD *head);
char *OperandsTable(FILE *hc12);
COD *searchCodop(COD *head,char *codop);

int main()
{
    COD *head = NULL,*found;
    char *codop = "BLE";
    CodopsList(head);
    if((found = searchCodop(head,codop)) == NULL)
        printf("COULDNT FIND CODOP");
    else
        printf("CODOP FOUND");

    return 0;
}


void searchEndofLine(FILE *fd)
{
    int car;
    while((car = fgetc(fd))!= '\n')
        ;
}

void ignoreSpaces(FILE *fd)
{
    int car;
    do
    {
        car = fgetc(fd);
    }while(car == '\t' || car == ' ');
}

void remove(char *c)
{
    char *ptr;
    if(((ptr=strchr(c,'\n'))!=NULL)||((ptr=strchr(c,'\t'))!=NULL)||((ptr=strchr(c,' '))!=NULL))
       *ptr = '\0';
}

void CodopsList(COD *head)
{
    int car;
    FILE *hc12;
    char *instruction;
    COD *last;
    if((hc12 = fopen("TABOP.txt","r"))!= NULL)
    {
        while((car = fgetc(hc12))!= EOF)
        {
            if(car != '\t')
            {
                instruction = OperandsTable(hc12);
                if(head == NULL)
                    head = createNodo(instruction);
                else
                {
                    last = lastElement(head);
                    insertEnd(instruction,last);
                }
            }
            else
               searchEndofLine(hc12);
        }
    }
    else
       printf("Error\n");
}

char *OperandsTable(FILE *hc12)
{
    int car,lon = 0,pos;
    char *c;
    fseek(hc12,-1,SEEK_CUR);
    pos = ftell(hc12);
    do
    {
        car = fgetc(hc12);
        lon++;
    }while(car != '\t');
    fseek(hc12,pos,SEEK_SET);
    c = (char*)calloc((lon+1),sizeof(char));
    fgets(c,lon+1,hc12);
    remove(c);
    searchEndofLine(hc12);
    return c;
}

void insertEnd(char *instruction,COD *last)
{
    last->next = createNodo(instruction);
    last->next->next = NULL;
    last = last->next;
}

COD *lastElement(COD *head)
{
    COD *ptr;
    ptr = head;
    while(ptr->next != NULL)
       ptr = ptr->next;
    return ptr;
}

COD *createNodo(char *instruction)
{
    COD *x;
    int t;
    t = strlen(instruction);
    x = (COD*)malloc(sizeof(COD));
    x->codigo = (char*)malloc((t+1)*sizeof(char));
    strcpy(x->code,instruction);
    x->next = NULL;
    return x;
}

COD *searchCodop(COD *head,char *codop)
{
    COD *ptr;
    for(ptr = head;ptr != NULL;ptr = ptr->next)
    {
        if(ptr->code == codop)
           return ptr;
    }
    return NULL;
}

Answer 1

您应该使用strcmp而不是比较两个数组指针。

在searchCodop而不是

if(ptr->code == codop)

DO

if (!strcmp(ptr->code, codop))

Answer 2

您正在调用指针作为值传递，而是使用按引用调用。为此，使用指针指针。像那样：

主要变化

CodopsList(head);

与

CodopsList(&head);

和

更改功能

void CodopsList(COD *head)

与

void CodopsList(COD **head)

在函数CodopsList中使用head作为* head

无法在链表上找到元素

2 个答案: