最近我一直在iPhone上玩一款名为《Scramble》的游戏。有些人可能知道这个游戏叫拼字游戏。从本质上讲，当游戏开始时，你会得到一个字母矩阵:
F X I E
A M L O
E W B X
A S T U
The goal of the game is to find as many words as you can that can be formed by chaining letters together. You can start with any letter, and all the letters that surround it are fair game, and then once you move on to the next letter, all the letters that surround that letter are fair game, except for any previously used letters. So in the grid above, for example, I could come up with the words LOB, TUX, SEA, FAME, etc. Words must be at least 3 characters, and no more than NxN characters, which would be 16 in this game but can vary in some implementations. While this game is fun and addictive, I am apparently not very good at it and I wanted to cheat a little bit by making a program that would give me the best possible words (the longer the word the more points you get).
(来源:boggled.org)
不幸的是，我不太擅长算法或它们的效率等等。我的第一次尝试使用一个像这样的字典(约2.3MB)，并进行线性搜索，试图匹配字典条目的组合。这需要花费很长时间来找到可能的单词，因为你每轮只有2分钟的时间，这是不够的。
我很有兴趣看看是否有任何Stackoverflowers可以提出更有效的解决方案。我主要是在寻找使用三大p的解决方案:Python、PHP和Perl，尽管任何使用Java或c++的东西也很酷，因为速度是至关重要的。
目前的解决方案:
Adam Rosenfield, Python， ~20岁
John Fouhy, Python， ~3秒
Kent Fredric, Perl， ~1s
Darius Bacon, Python， ~1s
rvarcher, VB。净,~ 1 s
Paolo Bergantino, PHP(实时链接)，~5s(本地~2s)
我意识到这个问题的时间来了又去了，但由于我自己正在研究一个求解器，并在谷歌搜索时偶然发现了这个，我想我应该发布一个参考，因为它似乎与其他一些问题有点不同。
我选择在游戏棋盘上使用平面数组，并从棋盘上的每个字母进行递归搜索，从有效邻居遍历到有效邻居，如果索引中的有效前缀是当前字母列表，则扩展搜索。而遍历当前单词的概念是进入板的索引列表，而不是组成单词的字母。在检查索引时，将索引转换为字母并完成检查。
索引是一个蛮力字典，有点像trie，但允许对索引进行python查询。如果单词'cat'和'cater'在列表中，你会在字典中看到:
d = { 'c': ['cat','cater'],
'ca': ['cat','cater'],
'cat': ['cat','cater'],
'cate': ['cater'],
'cater': ['cater'],
}
因此，如果current_word是'ca'，您就知道它是一个有效的前缀，因为'ca'在d中返回True(因此继续遍历板)。如果current_word是'cat'，那么你知道它是一个有效的单词，因为它是一个有效的前缀，并且d['cat']中的'cat'也返回True。
如果感觉这允许一些可读的代码，似乎不是太慢。像其他人一样，这个系统的费用是读取/构建索引。解这个板子相当麻烦。
代码在http://gist.github.com/268079。它是故意垂直和幼稚的，有很多明确的有效性检查，因为我想理解问题，而不是用一堆魔法或晦涩难懂的东西把它弄得乱七八糟。
import java.util.HashSet;
import java.util.Set;
/**
* @author Sujeet Kumar (mrsujeet@gmail.com) It prints out all strings that can
* be formed by moving left, right, up, down, or diagonally and exist in
* a given dictionary , without repeating any cell. Assumes words are
* comprised of lower case letters. Currently prints words as many times
* as they appear, not just once. *
*/
public class BoggleGame
{
/* A sample 4X4 board/2D matrix */
private static char[][] board = { { 's', 'a', 's', 'g' },
{ 'a', 'u', 't', 'h' },
{ 'r', 't', 'j', 'e' },
{ 'k', 'a', 'h', 'e' }
};
/* A sample dictionary which contains unique collection of words */
private static Set<String> dictionary = new HashSet<String>();
private static boolean[][] visited = new boolean[board.length][board[0].length];
public static void main(String[] arg) {
dictionary.add("sujeet");
dictionary.add("sarthak");
findWords();
}
// show all words, starting from each possible starting place
private static void findWords() {
for (int i = 0; i < board.length; i++) {
for (int j = 0; j < board[i].length; j++) {
StringBuffer buffer = new StringBuffer();
dfs(i, j, buffer);
}
}
}
// run depth first search starting at cell (i, j)
private static void dfs(int i, int j, StringBuffer buffer) {
/*
* base case: just return in recursive call when index goes out of the
* size of matrix dimension
*/
if (i < 0 || j < 0 || i > board.length - 1 || j > board[i].length - 1) {
return;
}
/*
* base case: to return in recursive call when given cell is already
* visited in a given string of word
*/
if (visited[i][j] == true) { // can't visit a cell more than once
return;
}
// not to allow a cell to reuse
visited[i][j] = true;
// combining cell character with other visited cells characters to form
// word a potential word which may exist in dictionary
buffer.append(board[i][j]);
// found a word in dictionary. Print it.
if (dictionary.contains(buffer.toString())) {
System.out.println(buffer);
}
/*
* consider all neighbors.For a given cell considering all adjacent
* cells in horizontal, vertical and diagonal direction
*/
for (int k = i - 1; k <= i + 1; k++) {
for (int l = j - 1; l <= j + 1; l++) {
dfs(k, l, buffer);
}
}
buffer.deleteCharAt(buffer.length() - 1);
visited[i][j] = false;
}
}
令人惊讶的是，没有人尝试使用PHP版本。
这是John Fouhy的Python解决方案的PHP版本。
虽然我从其他人的答案中得到了一些建议，但这主要是抄袭约翰的。
$boggle = "fxie
amlo
ewbx
astu";
$alphabet = str_split(str_replace(array("\n", " ", "\r"), "", strtolower($boggle)));
$rows = array_map('trim', explode("\n", $boggle));
$dictionary = file("C:/dict.txt");
$prefixes = array(''=>'');
$words = array();
$regex = '/[' . implode('', $alphabet) . ']{3,}$/S';
foreach($dictionary as $k=>$value) {
$value = trim(strtolower($value));
$length = strlen($value);
if(preg_match($regex, $value)) {
for($x = 0; $x < $length; $x++) {
$letter = substr($value, 0, $x+1);
if($letter == $value) {
$words[$value] = 1;
} else {
$prefixes[$letter] = 1;
}
}
}
}
$graph = array();
$chardict = array();
$positions = array();
$c = count($rows);
for($i = 0; $i < $c; $i++) {
$l = strlen($rows[$i]);
for($j = 0; $j < $l; $j++) {
$chardict[$i.','.$j] = $rows[$i][$j];
$children = array();
$pos = array(-1,0,1);
foreach($pos as $z) {
$xCoord = $z + $i;
if($xCoord < 0 || $xCoord >= count($rows)) {
continue;
}
$len = strlen($rows[0]);
foreach($pos as $w) {
$yCoord = $j + $w;
if(($yCoord < 0 || $yCoord >= $len) || ($z == 0 && $w == 0)) {
continue;
}
$children[] = array($xCoord, $yCoord);
}
}
$graph['None'][] = array($i, $j);
$graph[$i.','.$j] = $children;
}
}
function to_word($chardict, $prefix) {
$word = array();
foreach($prefix as $v) {
$word[] = $chardict[$v[0].','.$v[1]];
}
return implode("", $word);
}
function find_words($graph, $chardict, $position, $prefix, $prefixes, &$results, $words) {
$word = to_word($chardict, $prefix);
if(!isset($prefixes[$word])) return false;
if(isset($words[$word])) {
$results[] = $word;
}
foreach($graph[$position] as $child) {
if(!in_array($child, $prefix)) {
$newprefix = $prefix;
$newprefix[] = $child;
find_words($graph, $chardict, $child[0].','.$child[1], $newprefix, $prefixes, $results, $words);
}
}
}
$solution = array();
find_words($graph, $chardict, 'None', array(), $prefixes, $solution);
print_r($solution);
如果你想尝试的话，这里有一个实时链接。虽然在我的本地机器上需要大约2秒，但在我的web服务器上需要大约5秒。无论哪种情况，它都不是很快。尽管如此，它还是很可怕，所以我可以想象时间可以大大缩短。任何关于如何实现这一目标的建议都将不胜感激。PHP缺少元组，这使得坐标处理起来很奇怪，而且我无法理解到底发生了什么，这对我一点帮助都没有。
编辑:一些修复使它在本地少于1秒。
