1 // +build ignore
2
3 /*
4 Redistribution and use in source and binary forms, with or without
5 modification, are permitted provided that the following conditions are met:
6
7 * Redistributions of source code must retain the above copyright
8 notice, this list of conditions and the following disclaimer.
9
10 * Redistributions in binary form must reproduce the above copyright
11 notice, this list of conditions and the following disclaimer in the
12 documentation and/or other materials provided with the distribution.
13
14 * Neither the name of "The Computer Language Benchmarks Game" nor the
15 name of "The Computer Language Shootout Benchmarks" nor the names of
16 its contributors may be used to endorse or promote products derived
17 from this software without specific prior written permission.
18
19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
23 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 /*
33 * The Computer Language Shootout
34 * http://shootout.alioth.debian.org/
35 * Contributed by Heiner Marxen
36 *
37 * "fannkuch" for C gcc
38 *
39 * $Id: fannkuch.1.gcc.code,v 1.15 2009-04-28 15:39:31 igouy-guest Exp $
40 */
41
42 #include <stdio.h>
43 #include <stdlib.h>
44
45 #define Int int
46 #define Aint int
47
48 static long
fannkuch(int n)49 fannkuch( int n )
50 {
51 Aint* perm;
52 Aint* perm1;
53 Aint* count;
54 long flips;
55 long flipsMax;
56 Int r;
57 Int i;
58 Int k;
59 Int didpr;
60 const Int n1 = n - 1;
61
62 if( n < 1 ) return 0;
63
64 perm = calloc(n, sizeof(*perm ));
65 perm1 = calloc(n, sizeof(*perm1));
66 count = calloc(n, sizeof(*count));
67
68 for( i=0 ; i<n ; ++i ) perm1[i] = i; /* initial (trivial) permu */
69
70 r = n; didpr = 0; flipsMax = 0;
71 for(;;) {
72 if( didpr < 30 ) {
73 for( i=0 ; i<n ; ++i ) printf("%d", (int)(1+perm1[i]));
74 printf("\n");
75 ++didpr;
76 }
77 for( ; r!=1 ; --r ) {
78 count[r-1] = r;
79 }
80
81 #define XCH(x,y) { Aint t_mp; t_mp=(x); (x)=(y); (y)=t_mp; }
82
83 if( ! (perm1[0]==0 || perm1[n1]==n1) ) {
84 flips = 0;
85 for( i=1 ; i<n ; ++i ) { /* perm = perm1 */
86 perm[i] = perm1[i];
87 }
88 k = perm1[0]; /* cache perm[0] in k */
89 do { /* k!=0 ==> k>0 */
90 Int j;
91 for( i=1, j=k-1 ; i<j ; ++i, --j ) {
92 XCH(perm[i], perm[j])
93 }
94 ++flips;
95 /*
96 * Now exchange k (caching perm[0]) and perm[k]... with care!
97 * XCH(k, perm[k]) does NOT work!
98 */
99 j=perm[k]; perm[k]=k ; k=j;
100 }while( k );
101 if( flipsMax < flips ) {
102 flipsMax = flips;
103 }
104 }
105
106 for(;;) {
107 if( r == n ) {
108 return flipsMax;
109 }
110 /* rotate down perm[0..r] by one */
111 {
112 Int perm0 = perm1[0];
113 i = 0;
114 while( i < r ) {
115 k = i+1;
116 perm1[i] = perm1[k];
117 i = k;
118 }
119 perm1[r] = perm0;
120 }
121 if( (count[r] -= 1) > 0 ) {
122 break;
123 }
124 ++r;
125 }
126 }
127 }
128
129 int
main(int argc,char * argv[])130 main( int argc, char* argv[] )
131 {
132 int n = (argc>1) ? atoi(argv[1]) : 0;
133
134 printf("Pfannkuchen(%d) = %ld\n", n, fannkuch(n));
135 return 0;
136 }
137