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116 lines
2.9 KiB
C
116 lines
2.9 KiB
C
/*
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* fact.c
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*
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* Compute factorial of input integer
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*
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
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*
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* The Initial Developer of the Original Code is
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* Michael J. Fromberger.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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/* $Id: fact.c,v 1.3 2004/04/27 23:04:37 gerv%gerv.net Exp $ */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "mpi.h"
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mp_err mp_fact(mp_int *a, mp_int *b);
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int main(int argc, char *argv[])
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{
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mp_int a;
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mp_err res;
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if(argc < 2) {
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fprintf(stderr, "Usage: %s <number>\n", argv[0]);
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return 1;
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}
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mp_init(&a);
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mp_read_radix(&a, argv[1], 10);
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if((res = mp_fact(&a, &a)) != MP_OKAY) {
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fprintf(stderr, "%s: error: %s\n", argv[0],
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mp_strerror(res));
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mp_clear(&a);
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return 1;
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}
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{
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char *buf;
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int len;
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len = mp_radix_size(&a, 10);
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buf = malloc(len);
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mp_todecimal(&a, buf);
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puts(buf);
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free(buf);
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}
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mp_clear(&a);
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return 0;
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}
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mp_err mp_fact(mp_int *a, mp_int *b)
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{
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mp_int ix, s;
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mp_err res = MP_OKAY;
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if(mp_cmp_z(a) < 0)
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return MP_UNDEF;
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mp_init(&s);
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mp_add_d(&s, 1, &s); /* s = 1 */
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mp_init(&ix);
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mp_add_d(&ix, 1, &ix); /* ix = 1 */
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for(/* */; mp_cmp(&ix, a) <= 0; mp_add_d(&ix, 1, &ix)) {
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if((res = mp_mul(&s, &ix, &s)) != MP_OKAY)
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break;
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}
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mp_clear(&ix);
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/* Copy out results if we got them */
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if(res == MP_OKAY)
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mp_copy(&s, b);
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mp_clear(&s);
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return res;
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}
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