games/backgammon/common_source/odds.c

   1 /*-
   2  * Copyright (c) 1980, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. 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  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)odds.c   8.1 (Berkeley) 5/31/93
  30  * $FreeBSD: src/games/backgammon/common_source/odds.c,v 1.5 1999/11/30 03:48:26 billf Exp $
  31  * $DragonFly: src/games/backgammon/common_source/odds.c,v 1.3 2006/08/08 16:36:11 pavalos Exp $
  32  */
  33
  34 #include "back.h"
  35
  36 void
  37 odds(int r1, int r2, int val)
  38 {
  39         int i, j;
  40
  41         if (r1 == 0) {
  42                 for (i = 0; i < 6; i++)
  43                         for (j = 0; j < 6; j++)
  44                                 table[i][j] = 0;
  45                 return;
  46         } else {
  47                 r1--;
  48                 if (r2-- == 0) {
  49                         for (i = 0; i < 6; i++) {
  50                                 table[i][r1] += val;
  51                                 table[r1][i] += val;
  52                         }
  53                 } else {
  54                         table[r2][r1] += val;
  55                         table[r1][r2] += val;
  56                 }
  57         }
  58 }
  59
  60 int
  61 count(void)
  62 {
  63         int i, j, total;
  64
  65         total = 0;
  66         for (i = 0; i < 6; i++)
  67                 for (j = 0; j < 6; j++)
  68                         total += table[i][j];
  69         return (total);
  70 }
  71
  72 int
  73 canhit(int i, int c)
  74 {
  75         int j, k, b;
  76         int a, diff, place, addon, menstuck;
  77
  78         if (c == 0)
  79                 odds(0, 0, 0);
  80         if (board[i] > 0) {
  81                 a = -1;
  82                 b = 25;
  83         } else {
  84                 a = 1;
  85                 b = 0;
  86         }
  87         place = abs(25 - b - i);
  88         menstuck = abs(board[b]);
  89         for (j = b; j != i; j += a) {
  90                 if (board[j] * a > 0) {
  91                         diff = abs(j - i);
  92                         addon = place + ((board[j] * a > 2 || j == b) ? 5 : 0);
  93                         if ((j == b && menstuck == 1) &&
  94                             (j != b && menstuck == 0))
  95                                 for (k = 1; k < diff; k++)
  96                                         if (k < 7 && diff - k < 7 &&
  97                                             (board[i + a * k] * a >= 0 ||
  98                                              board[i + a * (diff - k)] >= 0))
  99                                                 odds(k, diff - k, addon);
 100                         if ((j == b || menstuck < 2) && diff < 7)
 101                                 odds(diff, 0, addon);
 102                 }
 103                 if (j == b && menstuck > 1)
 104                         break;
 105         }
 106         return (count());
 107 }