PHP - 2.580.210 indizi
In questo modo vengono rimosse l'ultima riga e colonna e l'angolo in basso a destra di ogni riquadro. Quindi cerca di cancellare ogni cella, facendo scorrere la scheda attraverso un semplice risolutore dopo ogni modifica per garantire che la scheda sia ancora inequivocabilmente risolvibile.
Gran parte del codice seguente è stato modificato da una delle mie vecchie risposte . printBoardusa 0s per celle vuote.
<?php
// checks each row/col/block and removes impossible candidates
function reduce($cand){
do{
$old = $cand;
for($r = 0; $r < 9; ++$r){
for($c = 0; $c < 9; ++$c){
if(count($cand[$r][$c]) == 1){ // if filled in
// remove values from row and col and block
$remove = $cand[$r][$c];
for($i = 0; $i < 9; ++$i){
$cand[$r][$i] = array_diff($cand[$r][$i],$remove);
$cand[$i][$c] = array_diff($cand[$i][$c],$remove);
$br = floor($r/3)*3+$i/3;
$bc = floor($c/3)*3+$i%3;
$cand[$br][$bc] = array_diff($cand[$br][$bc],$remove);
}
$cand[$r][$c] = $remove;
}
}}
}while($old != $cand);
return $cand;
}
// checks candidate list for completion
function done($cand){
for($r = 0; $r < 9; ++$r){
for($c = 0; $c < 9; ++$c){
if(count($cand[$r][$c]) != 1)
return false;
}}
return true;
}
// board format: [[1,2,0,3,..],[..],..], $b[$row][$col]
function solve($board){
$cand = [[],[],[],[],[],[],[],[],[]];
for($r = 0; $r < 9; ++$r){
for($c = 0; $c < 9; ++$c){
if($board[$r][$c]){ // if filled in
$cand[$r][$c] = [$board[$r][$c]];
}else{
$cand[$r][$c] = range(1, 9);
}
}}
$cand = reduce($cand);
if(done($cand)) // goto not really necessary
goto end; // but it feels good to use it
else return false;
end:
// back to board format
$b = [];
for($r = 0; $r < 9; ++$r){
$b[$r] = [];
for($c = 0; $c < 9; ++$c){
if(count($cand[$r][$c]) == 1)
$b[$r][$c] = array_pop($cand[$r][$c]);
else
$b[$r][$c] = 0;
}
}
return $b;
}
function add_zeros($board, $ind){
for($r = 0; $r < 9; ++$r){
for($c = 0; $c < 9; ++$c){
$R = ($r + (int)($ind/9)) % 9;
$C = ($c + (int)($ind%9)) % 9;
if($board[$R][$C]){
$tmp = $board[$R][$C];
$board[$R][$C] = 0;
if(!solve($board))
$board[$R][$C] = $tmp;
}
}}
return $board;
}
function generate($board, $ind){
// remove last row+col
$board[8] = [0,0,0,0,0,0,0,0,0];
foreach($board as &$j) $j[8] = 0;
// remove bottom corner of each box
$board[2][2] = $board[2][5] = $board[5][2] = $board[5][5] = 0;
$board = add_zeros($board, $ind);
return $board;
}
function countClues($board){
$str = implode(array_map('implode', $board));
return 81 - substr_count($str, '0');
}
function generateBoard($board){
return generate($board, 0);
}
function printBoard($board){
for($i = 0; $i < 9; ++$i){
echo implode(' ', $board[$i]) . PHP_EOL;
}
flush();
}
function readBoard($str){
$tmp = str_split($str, 9);
$board = [];
for($i = 0; $i < 9; ++$i)
$board[] = str_split($tmp[$i], 1);
return $board;
}
// testing
$n = 0;
$f = fopen('ppcg_sudoku_testing.txt', 'r');
while(($l = fgets($f)) !== false){
$board = readBoard(trim($l));
$n += countClues(generateBoard($board));
}
echo $n;