function solve()
{
$grid = makeEmptyGrid();
$list = [0, 1, 2, 3, 4, 5, 6, 7];
$tries = 0;
$solutions = 0;
foreach (permutations($list) as $permutation) {
$queens = [];
for ($i = 0; $i < 8; $i++) {
$queens[] = [$i, $permutation[$i]];
}
if (check($queens, $grid)) {
printSolution($queens);
$solutions++;
} else {
$tries++;
}
}
//print_r($solutions);
echo 'permutations tried: ' . $tries . '. solutions found: ' . $solutions;
}
function solution(array $A, $N)
{
$depthMax = 0;
$aqIterations = 0;
$arIterations = 0;
for ($i = 0; $i < $N - 2; $i++) {
$Ap = $A[$i];
$Aq = $Ap;
$k = $i;
while ($k < $N - 1 && $A[$k + 1] < $Aq) {
$Aq = $A[$k + 1];
$k++;
$aqIterations++;
}
$Ar = $Aq;
while ($k < $N - 1 && $A[$k + 1] > $Ar) {
$Ar = $A[$k + 1];
$k++;
$arIterations++;
}
$depthNow = min($Ap - $Aq, $Ar - $Aq);
if ($depthNow > $depthMax) {
$depthMax = $depthNow;
}
}
// echo "aqIterations: $aqIterations; arIterations: $arIterations\n";
return $depthMax;
}
$a = [0, 1, 3, -2, 0, 1, 0, -3, 2, 3];
printSolution('solution', [$a, count($a)]);
