Pascal Honore

<?php

function nslog($object){
    if(is_string($object) or is_numeric($object)){
        echo $object."\n";
    }else{
        echo serialize($object)."\n";
    }
}
class Cell {
    private $value = null;
    public function __construct(){

    }
    public function setValue($number){
        $this->value = $number;
    }
    public function value(){
        return $this->value;
    }
    public function resolveAttempt($board){
        if(is_null($this->value)){
            $possiblevalues = array();
            foreach(range(1,9) as $xvalue){
                $this->value = $xvalue;
                if($board->selfTest()){
                    $possiblevalues[] = $xvalue;
                }
            }
            if(count($possiblevalues)==1){
                $this->value = $possiblevalues[0];
            }else{
                $this->value = null;
            }
        }
    }
}
class Board {

    private $lines = array();

    public function __construct(){
        foreach(range(1,9) as $linenumber){
            $line = array();
            foreach(range(1,9) as $rownumber){
                $line[] = new Cell();
            }
            $this->lines[] = $line;
        }
    }
    public function lines(){
        return $this->lines;
    }
    public function columns(){
        $answer = array();
        foreach(range(1,9) as $columnnumber){
            $column = array();
            foreach(range(1,9) as $linenumber){
                $column[] = $this->lines[$linenumber-1][$columnnumber-1];
            }
            $answer[] = $column;
        }
        return $answer;
    }

        // $yindice = 0,1,2
    // $xindice = 0,1,2
    public function zone($yindice,$xindice){
        $answer = array();
        foreach(range(($yindice*3)+1,($yindice*3)+3) as $linenumber){
            foreach(range(($xindice*3)+1,($xindice*3)+3) as $columnnumber){
                $answer[] = $this->lines[$linenumber-1][$columnnumber-1];
            }
        }
        return $answer;
    }
    public function zones(){
        $answer = array();
        foreach(range(0,2) as $yindice){
            foreach(range(0,2) as $xindice){
                $answer[] = $this->zone($yindice,$xindice);
            }
        }
        return $answer;
    }
    public function allcells(){
        $answer = array();
        foreach(range(1,9) as $columnnumber){
            foreach(range(1,9) as $linenumber){
                $answer[] = $this->lines[$linenumber-1][$columnnumber-1];
            }
        }
        return $answer;
    }

    // line_number = 1,...,9 ; row_number = 1,...,9
    public function setValueForCell($line_number,$row_number,$value){
        $cell = $this->lines[$line_number-1][$row_number-1];
        $cell->setValue($value);
    }

    public function toString($separator){
        $string = '';
        foreach($this->lines() as $line){
            foreach($line as $cell){
                if($cell->value()){
                    $string .= $cell->value();
                }else{
                    $string .= $separator;
                }
            }
            $string .= "\n";
        }
        return $string;
    }

    public function selfTest(){
        if(!$this->selfTest_Lines()){
            return false;
        }
        if(!$this->selfTest_Columns()){
            return false;
        }
        if(!$this->selfTest_Zones()){
            return false;
        }
        return true;
    }
    public function selfTest_Lines(){
        // We need to establish that elements in lines occur at least once.
        foreach($this->lines() as $collection){
            if(!$this->selfTest_Collection($collection)){
                return false;
            }
        }
        return true;
    }
    public function selfTest_Columns(){
        // We need to establish that elements in columns occur at least once.
        foreach($this->columns() as $collection){
            if(!$this->selfTest_Collection($collection)){
                return false;
            }
        }
        return true;
    }
    public function selfTest_Zones(){
        // We need to establish that elements in square zones occur at least once.
        foreach($this->zones() as $collection){
            if(!$this->selfTest_Collection($collection)){
                return false;
            }
        }
        return true;
    }
    public function selfTest_Collection($collection){
        $already_found = array();
        foreach($collection as $cell){
            if($cell->value() and in_array($cell->value(),$already_found)){
                return false;
            }else{
                $already_found[] = $cell->value();
            }
        }
        return true;
    }

    public function onePassResolutionAttempt(){
        foreach($this->allcells() as $cell){
            $cell->resolveAttempt($this);
        }
    }
    public function isComplete(){
        $count = 0;
        foreach($this->allcells() as $cell){
            if($cell->value()){
                $count++;
            }
        }
        return ($count==81);
    }

}

$board = new Board();

$board->setValueForCell(1,1,1);
$board->setValueForCell(1,4,6);
$board->setValueForCell(1,6,4);
$board->setValueForCell(1,8,9);
$board->setValueForCell(1,9,3);

$board->setValueForCell(2,2,3);
$board->setValueForCell(2,4,8);
$board->setValueForCell(2,5,9);
$board->setValueForCell(2,8,2);

$board->setValueForCell(3,6,1);
$board->setValueForCell(3,7,4);
$board->setValueForCell(3,8,6);

$board->setValueForCell(4,3,3);
$board->setValueForCell(4,6,2);
$board->setValueForCell(4,7,7);

$board->setValueForCell(5,1,9);
$board->setValueForCell(5,4,7);
$board->setValueForCell(5,5,5);
$board->setValueForCell(5,6,8);
$board->setValueForCell(5,9,1);

$board->setValueForCell(6,3,5);
$board->setValueForCell(6,4,1);
$board->setValueForCell(6,7,2);

$board->setValueForCell(7,2,9);
$board->setValueForCell(7,3,1);
$board->setValueForCell(7,4,3);

$board->setValueForCell(8,2,7);
$board->setValueForCell(8,5,1);
$board->setValueForCell(8,6,5);
$board->setValueForCell(8,8,8);

$board->setValueForCell(9,1,5);
$board->setValueForCell(9,2,6);
$board->setValueForCell(9,4,4);
$board->setValueForCell(9,6,9);
$board->setValueForCell(9,9,2);

echo $board->toString('.');
while(!$board->isComplete()){
    $board->onePassResolutionAttempt();
}
nslog('');
echo $board->toString('.');