tcpl_ex-1-19.c

tcpl_ex-1-19.c

/*
 * Exercise 1-19. Write a function reverse(s) that reverses the character 
 * string s. Use it to write a program that reverses its input a line at a time.  
 *
 */

#include <stdio.h>

#define MAXLINE 1000
void reverse(char line[]);
int getline(char line[], int maxline);

int main(void)
{
	char line[MAXLINE];
	
	while (getline(line, MAXLINE) > 0)
	{
		reverse(line);
		printf("%s", line);
	}
	return 0;
}

int getline(char line[], int maxline)
{
	int c, i, j;
	i = j = 0;
	while ((c = getchar()) != EOF && c != '\n')
	{
		if (i < maxline - 2)
		{
			line[i++] = c;
		}
		j++;
	}
	if (c == '\n')
	{
		line[i++] = '\n';
		j++;
	}
	line[i] = '\0';
	return j;
}


void reverse(char line[])
{
	int i, j;
	char tmp;
	i = j = 0;
	while (line[j] != '\0')
		++j;
	if (line[--j] == '\n')
		--j;
	while (i < j)
	{
		tmp = line[i];
		line[i] = line[j];
		line[j] = tmp;
		--j;
		++i;
	}
}