Ex_4.13_reverse_string.c

/* a recursive version of revese(s); the string reverse function */

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

#define MAXLINE 100

int mgetline(char line[],int maxline);
void reverse(char s[]);

int main(void)
{
	char s[MAXLINE];

	mgetline(s,MAXLINE);

	reverse(s);

	printf("%s",s);
	
	return 0;
}

int mgetline(char s[],int lim)
{
	int i,c;

	for(i=0;i<lim-1 && (c=getchar())!=EOF && c!='\n';++i)
		s[i] = c;

	if(c=='\n')
		s[i++]='\n';

	s[i]='\0';
}

void reverse(char s[])
{
	void reverser(char s[],int i,int len);

	reverser(s,0,strlen(s));
}

/* reverser: reverse string s in place; recursive */

void reverser(char s[],int i,int len)
{
	int c,j;

	j = len - (i + 1);
	
	if( i < j )
	{
		c = s[i];
		s[i] = s[j];
		s[j] = c;

		reverser(s,++i,len);
	}
}