Question

Write a function 

               void reverse(char * s)

that reverses the string passed as an argument. Your code should use pointer arithmetic (it may increment and decrement pointers, but it may not use array indexing). 

Here is a piece of code that shows the behavior of reverse:

char buf[100];

strcpy(buf, “hello”);

reverse(buf);

printf(“%s\n”, buf);  // output should be olleh

Answer 1

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

void reverse(char * s) {
   char temp;
   char *last = s;
   while(*last) {
       last++;
   }
   last--;
   char *first = s;
   while(first < last) {
       temp = *first;
       *first = *last;
       *last = temp;
       first++;
       last--;
   }
}

int main() {
   char buf[100];
   strcpy(buf, "hello");
   reverse(buf);
   printf("%s\n", buf); // output should be olleh
   return 0;
}

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