reverse a character in array using recusion in C

Question

this is my recursion function

void reverseArray(char *str,int len)
    {
        char temp;
        if(len==(0.5*len))
        {
            return;
        }
        temp=*(str+len-1);
        *(str+len-1)=*str;
        *str=temp;
        reverseArray(str+1,len-1);
    }

iam trying to reverse the charcters but when i send {'1', '2', '3', '4', '5', '6','7'} to function i always get 7123456 only the last charcter become first the other not changing .

Answer 1

In this call

reverseArray(str+1,len-1);

the second argument is incorrect. You have to write

reverseArray(str+1,len-2);

Also instead of this condition

if(len==(0.5*len))

it is much better to write

if ( len < 2 )

The function can look the following way

void reverseArray( char *str, size_t n )
{
    if ( !( n < 2 ) )
    {
        char tmp = *str;
        *str = *( str + n - 1 );
        *( str + n - 1 ) = tmp;

        reverseArray( str + 1, n - 2 );
    }
}

Or

char * reverseArray( char *str, size_t n )
{
    if ( !( n < 2 ) )
    {
        char tmp = *str;
        *str = *( str + n - 1 );
        *( str + n - 1 ) = tmp;

        reverseArray( str + 1, n - 2 );
    }

    return str;
}

Pay attention that the function strlen or the operator sizeof returns a value of the type size_t. This type you should use to specify the length of a character array instead of the type int.

For example the last function can be called like

char str[] = "Hello World!";
puts( reverseArray( str, strlen( str ) ) );