Answer to Question #198587 in C for ABDULQADIR BUTT

Question

Write a function called str_rev() that takes a pointer to a string as input and reverses the string in-place (this change should be reflected in the original string that was passed to the function, not to a copy of the string). No library functions for string reversal should be used. The function should also return a pointer to the reversed string.

Function prototype is given below:

char * str_rev(char * str);

Answer 1

#include <stdio.h>

char* str_rev(char* str)
{
    char* begin = str;
    char* end   = str;

    while(*end != 0)
    {
        ++end;
    }   

    for(--end; begin < end; ++begin, --end)
    {
        char tmp = *begin;
        *begin = *end;
        *end = tmp;
    }
    
    return str;
}

int main()
{
    char* data = "Test string";
    printf("Source: '%s'\n", data);
    printf("Result: '%s'\n", str_rev(data));
    return 0;
}