Reverse_letters.c

//program to reverse letters in words

#include <stdio.h>
#include <string.h>
void reverse(char str[], int start, int end)
{
	char tmp;

	while (start <= end)
	{
		tmp = str[start];
		str[start] = str[end];
		str[end] = tmp;
		start++;
		end--;
	}
}

void reverse_letters(char str[], int start, int end)
{
	int w_start, w_end;
	for (w_start = w_end = start; w_end < end; w_end++)
	{
		if (str[w_end] == ' ')
			continue;
		w_start = w_end;
		while (str[w_end] != ' ' && w_end <= end)
			w_end++;
		w_end--;
		reverse(str, w_start, w_end);
	}
}
int main(void)
{
	char str[20];
	int i, j;

	printf("Enter a string : ");
	gets(str);
	puts(str);
	reverse_letters(str, 0, strlen(str) - 1);
	puts(str);

	return 0;
}