CC1.2 Implement a function void reverse(char* str) in C or C++ which reverses a null-terminated string.

ReverseString.cpp

/* idea:    using 2 pointers respectively point to the start and the end of the string, 
            swap the value they point to, then move the pointers iteratively.
   time:    complexity: O(n)
   space    complexity: O(1)
*/

void reverse(char* str)
{
	if(!str)
		return;

	char *left = str, *right = str + strlen(str) - 1;
	while(left < right)
	{
		swap(*left, *right);    // built by stl, must include <algorithm>
		left++;
		right--;
	}
}