Question

我正在使用链接列表来保存表示ASCII字符的结构。我能够从文件中读取输入并打印回去，所以我知道我有需要的数据。在将节点添加到列表中并尝试打印列表以确保节点被填充后，程序突然结束，但是我不明白为什么。我的输入文件目前只有一行。（例如111B1111）

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

#ifndef NULL
    #define NULL 0
#endif

// Define a struct to be used in the linked list
typedef struct tape {
    int ch;
    struct tape *next_rec;
    struct tape *prev_rec;
} tape;

// Typedef for the structure pointer
typedef tape *TAPEPTR;

// Define a struct to hold the transition instructions
typedef struct instruction {
    int write;
    int direction;
    int new_state;
} instruction;

// Variables
int num_states;
int start_state;
int end_state;
char filename[20];
FILE *fp;

// Add ASCII character to linked list
TAPEPTR build_list(int size, char *input) {
    TAPEPTR head = NULL;
    int i = 0;
    int ch;
    while (i++ < size) {
        ch = input[i];

        TAPEPTR new_rec = NULL;
        TAPEPTR tmp_rec = NULL;
        TAPEPTR prev_rec = NULL;

        // Allocate memory for the list item
        new_rec = (TAPEPTR)malloc(sizeof(tape));
        if (!new_rec) {
            printf("\nUnable to allocate memory!\n");
            exit(1);
        }

        // Set the new link's data
        new_rec->ch = ch;
        new_rec->next_rec = NULL;
        new_rec->next_rec = NULL;

        //Adding first item to the list
        if (head == NULL) {
            head = new_rec;
            new_rec->next_rec = NULL;
            new_rec->prev_rec = NULL;
        } else {
            // Adding item at the end of the list
            tmp_rec = head->next_rec;
            prev_rec = head;
            while (tmp_rec->next_rec != NULL) {
                tmp_rec = tmp_rec->next_rec;
                prev_rec = prev_rec->next_rec;
            }
            tmp_rec->next_rec = new_rec;
            new_rec->prev_rec = tmp_rec;
            new_rec->next_rec = NULL;

        }
    }
    return head;
}

// Display the linked list
void show_list(TAPEPTR head)  {
    TAPEPTR cur_ptr = head;
    while (cur_ptr != NULL) {
        printf("\n%d", cur_ptr->ch);
    }
    cur_ptr = cur_ptr->next_rec;
}


// Setup turing machine
void load(FILE* fp) {
    char buf[256];
    // Read text until newline 
    fscanf(fp, "%[^\n]", buf);
    int length = strlen(buf);
    printf("Data from the file: \n%s", buf);

    // Create a doubly-linked list and store nodes as type struct tape
    TAPEPTR head = build_list(length, buf);

    // Print out the linked list
    show_list(head);



    //fclose(fp);

}


int main(void) {

    // Ask the user for the input file
    printf("\nEnter the name of the input file: ");
    gets(filename);

    // Open the input file for reading
    if ((fp = fopen(filename, "r")) == NULL) {
        fprintf(stderr, "Error opening file.\n");
        exit(1);
    }

    // Build the Turing Machine
    load(fp);

    return 0;
}

为什么我的程序在打印出链表之前终止？

0 个答案: