strrev.c

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

char* strrev(char* start, char* end)
{
	char *i = start;
	char *j = end;

	while (i < j)
	{
		*i ^= *j;
		*j ^= *i;
		*i ^= *j;

		++i;
		--j;
	}

	return start;
}

int main()
{
	char str[50] = "My Name Is";
	int length = strlen(str);

	printf("Input: %s\n", str);

	// Reverse the string
	strrev(str, str+length-1);
	printf("Reversed Input: %s\n", str);

	char *start_of_word = str;

	// Reverse each word
	int k;
	for (k = 0; k < length; k++)
	{
		if (str[k] == ' ' || str[k] == '\0')
		{
			strrev(start_of_word, str + k - 1);
			start_of_word = str + k + 1;
		}
	}

	printf("Output: %s\n", str);
}