--- In [EMAIL PROTECTED], "Trilokesh"
<[EMAIL PROTECTED]> wrote:
>
>
> Hi all,
>
> I want to write a program,which will find all the
> "permutation" of a given string.
> please help in solving problem,is this problem can
> be solve by recursion.
/* ---------------------------------------------------- */
/* Nth Permutation Generator. */
/* Copyright (c) LJW December 4, 2000. */
/* This is based on the permutation generator that was */
/* described in the notes published by L. J. Woodrum */
/* in 1970. */
/* ---------------------------------------------------- */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int factorial(int N) {
int i, n;
for (i = 1, n = N; n > 0; n--) i = i * n;
return(i);
}
/* ----------------------------------------------------- */
/* Given L, the length of the permutation, N, the number */
/* of the permutation N in the list, compute permutation */
/* number N at the int array P. */
/* ----------------------------------------------------- */
void perm(int L, int N, int *P) {
int i,j,n;
if (L <= 1) P[0] = 0;
return;
}
/* ----------------------------------------------------- */
/* Compute the mixed radix representation of the number N */
/* in the radix L, L-1, ... 2, 1. */
/* Do this by repeatedly dividing by 1, 2, 3, .. to L-1. */
/* ----------------------------------------------------- */
P[L - 1] = 0;
for (i = L-2, n = 1; i >= 0; i--) {
n = n + 1;
P[i] = N % n;
N = N / n;
}
/* ----------------------------------------------------- */
/* Now generate the permutation at the array P. */
/* ----------------------------------------------------- */
for(i = L - 1; i > 0; ) {
i--;
n = P[i];
for (j = i + 1; j < L; j++) {
if (n <= P[j]) P[j]++;
}
}
}
int main(int argc, char **argv) {
int P[16];
int i,f;
int L;
int N;
#define Uchr unsigned char
Uchr string[128];
Uchr *str;
str = &string[0];
if (argc < 2) {
fprintf(stderr, "Not enough arguments. Syntax: perms
character_string\n");
exit(7);
}
L = strlen(argv[1]);
str[L] = '\0';
f = factorial(L);
for (N = 0; N < f; N++) {
// Going to get the mixed radix representation for length %d and
//permutation #%d\n",L,N);
perm(L,N,P);
for (i = 0; i < L; i++) {
str[i] = (argv[1])[P[i]];
}
fprintf(stdout, "%s\n", str);
}
return(0);
}
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