Core keeps dumping when trying to reverse array using a function to swap values of 2 pointers-CodePudding

#include<stdio.h>

int main() {
    /* read integer array */
    int n, i;
    scanf("%d", &n);
    int *a = (int *)malloc(n * sizeof(int));
    for (i = 0; i < n; i  ) {
        scanf("%d", &a[i]);
    }
    
    /* reverse the array */
    for (i = 0; i < n / 2; i  ) {
        exchange(a[i], a[n - i - 1]);
    }

    /* print the array */
    for (i = 0; i < n; i  ) {
        printf("%d ", a[i]);
    }

    /* free the memory */
    free(a);

    return;
    
}

/* write a function that takes two pointers of two intergers and then exchanges the values
in those locations */
void exchange(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

This is the code, the function exchange tries to exchange the values of the integers which these two pointers are pointing to. Keeps dumping the core.

CodePudding user response：

In this call of the function exchange

exchange(a[i], a[n - i - 1]);

the both arguments have the type int while the function expects arguments of the type int *.

You need to call the function like

exchange( a   i, a   n - i - 1);

CodePudding user response：

You need to send address values for exchange functions since arguments of it are declared as pointers. Therefore, you need to change this line

exchange(a[i], a[n - i - 1]);

to this line because as I mentioned it expects addresses.

exchange(&a[i], &a[n - i - 1]);

CodePudding user response：

A nicer way would be passing the whole array and indexes to swap.

Like this: TRY IT ONLINE

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

void exchange(int **arr, int n1, int n2);

int main() {
    /* read integer array */
    int n, i;
    scanf("%d", &n);
    int *a = (int *)malloc(n * sizeof(int));
    for (i = 0; i < n; i  ) {
        scanf("%d", &a[i]);
    }
    
    /* reverse the array */
    for (i = 0; i < n / 2; i  ) {
        exchange(&a, i, n - i - 1);
    }

    /* print the array */
    for (i = 0; i < n; i  ) {
        printf("%d ", a[i]);
    }

    /* free the memory */
    free(a);

    return 0;
    
}

/* write a function that takes two pointers of two intergers and then exchanges the values
in those locations */
void exchange(int **arr, int n1, int n2) {
    int temp = (*arr)[n1];
    (*arr)[n1] = (*arr)[n2];
    (*arr)[n2] = temp;
}