Linked lists, operations with parameter

问题

I'm trying to implement program in with i can create ~arbitrary number of singly linked lists dynamically and perform operations on particular one (defined by parameter). I create dynamic array of head pointers so that i can refer to the certain head node defined by paramater(index of an array + 1). Parameter is just (1,2,3..number of lists). So far I have managed to implement only initialise and push function but the program after complilation doesn't work as expected. Where is the problem?

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

#define CHUNK 10

typedef struct
{
    char *str;
    struct node *next;
} node;


node *initialise(node **array, int *amount_of_lists);
void push(node **array, int *amount_of_lists);
char *getString(void);

int main()
{
    node **heads = NULL; //initially null, pointer to the dynamic array of head pointers
    int amount_of_lists = 0;
    int *no_of_heads = &amount_of_lists;

    initialise(heads, no_of_heads);
    initialise(heads, no_of_heads);
    push(heads, no_of_heads);
    push(heads, no_of_heads);

    return 0;
}

node *initialise( node **array, int *amount_of_lists )  /*reallocate memory for another head pointer ans return the pointer to node*/
{
    ++(*amount_of_lists);
    printf("\n%d", *amount_of_lists);
    array = (node**)realloc(array, sizeof(node*)*(*amount_of_lists));
    return array[(*amount_of_lists) - 1] = malloc(sizeof(node));
}

int readParameter(int *amount_of_lists)
{
    int parameter = 0, control = 0;
    bool repeat = 0;
    do
    {
        if(repeat)
        {
            printf("\nWrong parameter, try again.");
        }
        printf("\n Enter list parameter: ");
        control = scanf("%d", &parameter);
        fflush(stdin);
        repeat = 1;
    }
    while( control != 1 || parameter < 1 || parameter > (*amount_of_lists) );

    return parameter;
}

void push(node **array, int *amount_of_lists)
{
    int parameter = readParameter(amount_of_lists) - 1;
    node *temp = array[parameter];
    array[parameter] = malloc(sizeof(node));
    array[parameter] -> next = temp;
    array[parameter] -> str = getString();
}

char *getString(void)
{
    char *line = NULL, *tmp = NULL;
    size_t size = 0, index = 0;
    int ch = EOF;

    while (ch)
    {
        ch = getc(stdin);

        /* Check if we need to stop. */
        if (ch == EOF || ch == '\n')
            ch = 0;

        /* Check if we need to expand. */
        if (size <= index)
        {
            size += CHUNK;
            tmp = realloc(line, size);
            if (!tmp)
            {

                free(line);
                line = NULL;
                break;
            }
            line = tmp;
        }

        /* Actually store the thing. */
        line[index++] = ch;
    }

    return line;
}

回答1:

As BLUEPIXY somewhat crypticly hinted at in his comment 1), in order to modify main()'s heads in initialise(), you have to pass heads by reference to initialise(), i. e. change

    initialise(heads, no_of_heads);
    initialise(heads, no_of_heads);

    initialise(&heads, no_of_heads);
    initialise(&heads, no_of_heads);

consequently

node *initialise( node **array, int *amount_of_lists )

changes to

node *initialise(node ***array, int *amount_of_lists)

and inside array changes to *array, i. e.

    *array = realloc(*array, sizeof(node *) * *amount_of_lists);
    return (*array)[*amount_of_lists - 1] = malloc(sizeof(node));

来源：https://stackoverflow.com/questions/30686400/linked-lists-operations-with-parameter

标签

singly-linked-list