backgammon/common_source/odds.c

   1 /*      $NetBSD: odds.c,v 1.4 1997/10/10 08:59:46 lukem Exp $   */
   2
   3 /*
   4  * Copyright (c) 1980, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #ifndef lint
  38 #if 0
  39 static char sccsid[] = "@(#)odds.c      8.1 (Berkeley) 5/31/93";
  40 #else
  41 __RCSID("$NetBSD: odds.c,v 1.4 1997/10/10 08:59:46 lukem Exp $");
  42 #endif
  43 #endif /* not lint */
  44
  45 #include "back.h"
  46
  47 void
  48 odds(r1, r2, val)
  49         int     r1, r2, val;
  50 {
  51         int     i, j;
  52
  53         if (r1 == 0) {
  54                 for (i = 0; i < 6; i++)
  55                         for (j = 0; j < 6; j++)
  56                                 table[i][j] = 0;
  57                 return;
  58         } else {
  59                 r1--;
  60                 if (r2-- == 0) {
  61                         for (i = 0; i < 6; i++) {
  62                                 table[i][r1] += val;
  63                                 table[r1][i] += val;
  64                         }
  65                 } else {
  66                         table[r2][r1] += val;
  67                         table[r1][r2] += val;
  68                 }
  69         }
  70 }
  71
  72 int
  73 count()
  74 {
  75         int     i;
  76         int     j;
  77         int     total;
  78
  79         total = 0;
  80         for (i = 0; i < 6; i++)
  81                 for (j = 0; j < 6; j++)
  82                         total += table[i][j];
  83         return (total);
  84 }
  85
  86 int
  87 canhit(i, c)
  88         int     i, c;
  89 {
  90         int     j, k, b;
  91         int     a, diff, place, addon, menstuck;
  92
  93         if (c == 0)
  94                 odds(0, 0, 0);
  95         if (board[i] > 0) {
  96                 a = -1;
  97                 b = 25;
  98         } else {
  99                 a = 1;
 100                 b = 0;
 101         }
 102         place = abs(25 - b - i);
 103         menstuck = abs(board[b]);
 104         for (j = b; j != i; j += a) {
 105                 if (board[j] * a > 0) {
 106                         diff = abs(j - i);
 107                         addon = place + ((board[j] * a > 2 || j == b) ? 5 : 0);
 108                         if ((j == b && menstuck == 1) &&
 109                             (j != b && menstuck == 0))
 110                                 for (k = 1; k < diff; k++)
 111                                         if (k < 7 && diff - k < 7 &&
 112                                             (board[i + a * k] * a >= 0 ||
 113                                                 board[i + a * (diff - k)] >= 0))
 114                                                 odds(k, diff - k, addon);
 115                         if ((j == b || menstuck < 2) && diff < 7)
 116                                 odds(diff, 0, addon);
 117                 }
 118                 if (j == b && menstuck > 1)
 119                         break;
 120         }
 121         return (count());
 122 }