/* -*-c,save-*- */
/*
 * rperm.c - random permutate a string
 * Robert Heller. Created: Sun Mar 9, 1986 16:13:17.62
 * Last Mod: 
 * 
 * (c) Copyright 1986 by Robert Heller
 *     All Rights Reserved
 * 
 * 
 */

#include <stdio.h>

#define LOCAL static

/* #define DEBUG /* */
#ifdef DEBUG
#define LOCAL /* static */
#endif

rpermute(input,output)
char *input,*output;
{
    register char *p1,*p2;
    register int len,indx,t;

    p2 = output;
    *p2 = '\0';
    for (p1=input,len=0;*p1 != '\0';p1++,len++) {
	t = *p1;
	indx = rand() % (len+1);
#ifdef DEBUG
	printf("***len=%d, indx=%d, t=%c\n",len,indx,t);
#endif
	pushdown(p2+indx,len-indx);
#ifdef DEBUG
	printf("***(before insert)p2=%s\n",p2);
#endif
	*(p2+indx) = t;
#ifdef DEBUG
	printf("***(after insert)p2=%s\n",p2);
#endif
	}
    output[len] = '\0';
    }
char *a_rpermute(input)
register char *input;
{
    register char *output;
    char *malloc();

    output = malloc(strlen(input)+1);
    if (output == NULL) {
	perror("rpermute");
	abort(0);
	}
    rpermute(input,output);
    return(output);
    }
LOCAL pushdown(start,len)
register char *start;
register int len;
{
    register char *eos;
#ifdef DEBUG
    printf("***(pushdown): len=%d, start=%s\n",len,start);
#endif
    eos = start+len;
    while (len-- > 0) {
	*eos = *(eos-1);
	eos--;
#ifdef DEBUG
    printf("***(pushdown loop): len=%d, start=%s\n",len,start);
#endif
	}
    }