112 lines
2.1 KiB
C
112 lines
2.1 KiB
C
/* Copyright (c) 1984 AT&T */
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/* All Rights Reserved */
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/* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T */
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/* The copyright notice above does not evidence any */
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/* actual or intended publication of such source code. */
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/* #ident "@(#)factor:factor.c 1.2" */
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#ident "$Header: /proj/irix6.5.7m/isms/eoe/cmd/factor/RCS/factor.c,v 1.6 1996/08/23 21:03:29 livesey Exp $"
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/* factor COMPILE: cc -O factor.c -s -i -lm -o factor */
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/*
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* works up to 14 digit numbers, this limit is due to strod (used in scanf) in
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* can only handle 14 digits. Otherwise it returns inaccurate values.
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* running time is proportional to sqrt(n)
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* accepts arguments either as input or on command line
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* 0 input terminates processing
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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void try(double arg);
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double nn, vv;
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double huge = 1.0e14;
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double sq[] = {
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10, 2, 4, 2, 4, 6, 2, 6,
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4, 2, 4, 6, 6, 2, 6, 4,
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2, 6, 4, 6, 8, 4, 2, 4,
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2, 4, 8, 6, 4, 6, 2, 4,
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6, 2, 6, 6, 4, 2, 4, 6,
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2, 6, 4, 2, 4, 2,10, 2,
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};
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main(int argc, char **argv)
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{
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int test = 1;
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int ret;
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register j;
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double junk, temp;
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double fr;
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double ii;
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if(argc > 2){
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printf("Usage: factor number\n");
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exit(1);
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}
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if(argc == 2){
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ret = sscanf(argv[1], "%lf", &nn);
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test = 0;
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printf("%.0f\n", nn);
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goto start;
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}
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while(test == 1){
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ret = scanf("%lf", &nn);
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start:
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if((ret<1) || (nn == 0.0)){
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exit(0);
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}
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if((nn<0.0) || (nn>huge)){
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printf("Ouch! Value not between 1 and %.lf\n",huge);
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continue;
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}
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fr = modf(nn, &junk);
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if(fr != 0.0){
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printf("Not an integer!\n");
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continue;
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}
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vv = 1. + sqrt(nn);
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try(2.0);
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try(3.0);
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try(5.0);
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try(7.0);
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ii = 1.0;
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while(ii <= vv){
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for(j=0; j<48; j++){
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ii += sq[j];
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retry:
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modf(nn/ii, &temp);
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if(nn == temp*ii){
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printf(" %.0f\n", ii);
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nn = nn/ii;
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vv = 1 + sqrt(nn);
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goto retry;
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}
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}
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}
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if(nn > 1.0){
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printf(" %.0f\n", nn);
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}
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printf("\n");
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}
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return 0;
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}
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void
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try(double arg)
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{
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double temp;
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retry:
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modf(nn/arg, &temp);
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if(nn == temp*arg){
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printf(" %.0f\n", arg);
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nn = nn/arg;
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vv = 1 + sqrt(nn);
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goto retry;
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}
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return;
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}
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