CareerCup

Hello,

I just picked up "Cracking the Coding Interview" and I started working through the first chapter's questions. I typed in the author's solution to question 1.2 and I can't see how this would work. The solution attempts to reverse a string, in place, by decrementing a pointer positioned at the last char and incrementing a pointer at the beginning of a string until the pointers meet in the middle.

The solution is as follows:

{{#include <stdio.h>

void reverse(char *str){
char *end = str;
char tmp;

while(*end){
++end;
}
--end;

while(str < end){
tmp = *str;
*str++ = *end;
*end-- = tmp;
}
printf("str: %s\n",str);
printf("end: %s\n",end);
}
}}

I tested this solution like so:

{{int main(int argc, const char * argv[])
{

char mystring[] = "hello";
reverse(mystring);
return 0;
}
}}

This does not work. The issue is with condition in the while loop. Control is returned from the loop when both "str" and "end" are equal. In my above example the printf statements will output

str: leh
end: leh

This makes sense. It seems that the condition is expecting the values of str & end to be ordinal positions ?? Am I over looking something obvious?

Thanks!