mirror of
https://github.com/rn10950/RetroZilla.git
synced 2024-11-14 11:40:13 +01:00
83 lines
1.4 KiB
C
83 lines
1.4 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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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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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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