Reversing Array in C?

Question

Hi i trying to implement a reverse array code but it doesnt seem to work and im really not sure why. The For loop just doesnt seem to work. I dont know why because the logic seems pretty right to me.

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

void reverse(char, int);

int main()
{
    char a[100];
    gets(a);

    reverse(a, strlen(a)-1);

    printf("%s\n",a);
    getchar();
    getchar();
    getchar();
    return 0;
}

void reverse(char ar[], int n)
{
    char c;
    int i = 0;
    printf("n = %d" , n);
    for ( i = 0; i >= n ; i++){
        c = ar[i];
        ar[i] = ar[n];
        ar[n] = c;
        printf("Processed");
        n--;}

}


/*
if (begin >= n)
return;

c          = *(x+begin);
*(x+begin) = *(x+n);
*(x+n)   = c;
offs = x++;
printf("Begin = %d   ,  n = %d, offs = %p  \n", begin, n, offs);
reverse(x, ++begin, --n); */

Solution 1

void reverse(char, int);  //declaration wrong

void reverse(char[], int);
                 ^^^ 

---

Your loop

for ( i = 0; i >= n ; i++) // this fails i=0, n=some size

should be

for ( i = 0; i <= n ; i++)

Avoid using gets() use fgets() instead.

Solution 2

for loop condition should be 'i < n'. and prototype declaration should match.

Comments

[hasanoviz]

do changes to this array inside the reverse function actually take effect afterwards? because, not the pointer is sent as parameter.

[WhozCraig]

@hasanovh Arrays are simply named addresses in C. Said-address is passed as a pointer value to the function. They are the exception to the pass-by-value idiom of C, but not really. Their "value" is their address. Most engineers call this address synonymousness "pointer decay", though I find the tagline generally irritating, as the word "decay" appears exactly once in the entire C99 standard, and its appearance has absolutely nothing to do with passing arrays to functions.

[Gangadhar]

@hasanovh AS WhozCraig said Arrays are simply named addressed in C. Said-address is passed as a pointer value to the function adding this example to WhozCriag explanation. ideone.com/B9e5hG

[Dmitri]

He doesn't need to divide n in half because he decrements it in the loop, though it's easy to miss that.

[Jason Warner]

Breaking code into smaller units is a good practice, but that doesn't really answering the question. Plus, this is kind of implied in stackoverflow.com/a/42063309/4234794 by use of a macro.