games/backgammon/common_source/odds.c

   1 /*      $NetBSD: odds.c,v 1.6 2005/07/01 01:12:39 jmc 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. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * 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 REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #ifndef lint
  34 #if 0
  35 static char sccsid[] = "@(#)odds.c      8.1 (Berkeley) 5/31/93";
  36 #else
  37 __RCSID("$NetBSD: odds.c,v 1.6 2005/07/01 01:12:39 jmc Exp $");
  38 #endif
  39 #endif /* not lint */
  40
  41 #include "back.h"
  42
  43 void
  44 odds(int r1, int r2, int val)
  45 {
  46         int     i, j;
  47
  48         if (r1 == 0) {
  49                 for (i = 0; i < 6; i++)
  50                         for (j = 0; j < 6; j++)
  51                                 table[i][j] = 0;
  52                 return;
  53         } else {
  54                 r1--;
  55                 if (r2-- == 0) {
  56                         for (i = 0; i < 6; i++) {
  57                                 table[i][r1] += val;
  58                                 table[r1][i] += val;
  59                         }
  60                 } else {
  61                         table[r2][r1] += val;
  62                         table[r1][r2] += val;
  63                 }
  64         }
  65 }
  66
  67 int
  68 count(void)
  69 {
  70         int     i;
  71         int     j;
  72         int     total;
  73
  74         total = 0;
  75         for (i = 0; i < 6; i++)
  76                 for (j = 0; j < 6; j++)
  77                         total += table[i][j];
  78         return (total);
  79 }
  80
  81 int
  82 canhit(int i, int c)
  83 {
  84         int     j, k, b;
  85         int     a, diff, place, addon, menstuck;
  86
  87         if (c == 0)
  88                 odds(0, 0, 0);
  89         if (board[i] > 0) {
  90                 a = -1;
  91                 b = 25;
  92         } else {
  93                 a = 1;
  94                 b = 0;
  95         }
  96         place = abs(25 - b - i);
  97         menstuck = abs(board[b]);
  98         for (j = b; j != i; j += a) {
  99                 if (board[j] * a > 0) {
 100                         diff = abs(j - i);
 101                         addon = place + ((board[j] * a > 2 || j == b) ? 5 : 0);
 102                         if ((j == b && menstuck == 1) ||
 103                             (j != b && menstuck == 0))
 104                                 for (k = 1; k < diff; k++)
 105                                         if (k < 7 && diff - k < 7 &&
 106                                             (board[i + a * k] * a >= 0 ||
 107                                                 board[i + a * (diff - k)] >= 0))
 108                                                 odds(k, diff - k, addon);
 109                         if ((j == b || menstuck < 2) && diff < 7)
 110                                 odds(diff, 0, addon);
 111                 }
 112                 if (j == b && menstuck > 1)
 113                         break;
 114         }
 115         return (count());
 116 }