Description:

A number is a self-describing number when (assuming digit positions are labeled 0 to N-1), the digit in each position is equal to the number of times that that digit appears in the number.

Input sample:

The first argument is the pathname to a file which contains test data, one test case per line. Each line contains a positive integer. Each line is in the format: N i.e. a positive integer eg.

2020
22
1210

Output sample:

If the number is a self-describing number, print out a 1. If not, print out a 0 eg.

1
0
1

For the curious, here’s how 2020 is a self-describing number: Position ’0′ has value 2 and there is two 0 in the number. Position ’1′ has value 0 because there are not 1′s in the number. Position ’2′ has value 2 and there is two 2. And the position ’3′ has value 0 and there are zero 3′s.

My Solution:

#!/usr/bin/php
<?php

$file;
(isset($argv[1])) ? $file = $argv[1]:exit("Must provide a file");


/*  FileHandler:
    Wrap some common read operations.
*/
class FileHandler { 

    /*  readByLine
        Use: FileHandler::readByLine('filePath',true);
    */
    public static function readByLine($file /*Full file path*/,$rtrim /*Boolean*/) { // Return an array of lines
        $lines = array();
        (ISSET($rtrim) && ($rtrim == true)) ? $rtrim = true: $rtrim = false;
        $file_handle = fopen($file, "r");
        while (!feof($file_handle)) {
            $line = fgets($file_handle);
            if ($rtrim) { $line = rtrim($line); }
            array_push($lines,$line);
        }
        fclose($file_handle);
        return $lines;
    }
}


$contents = FileHandler::readByLine($file,true);
foreach ($contents as $line) {
    $ints = str_split($line);
    $l = count($ints);
    $state = 1;
    for ($i = 0; $i < $l; $i++) {
        $c = 0;
        preg_match_all("/$i/",$line,$m,PREG_OFFSET_CAPTURE);
        if (isset($m[0])) { $c = count($m[0]); }
        if ($c != $ints[$i]) {
            $state = 0;
            break;
        }
    }
    print $state."\n";
}


exit;
?>

Description:

Spiral Printing: Write a function to print a 2-D array (n x m) in spiral order (clockwise). For example, consider the following input:

1 2 3
4 5 6
7 8 9

Then the output of your program should be:

1 2 3 6 9 8 7 4 5

My Solution:

I was bored with the multiple-iterator approach commonly used to solve this puzzle. I received this test when applying for a JavaScript engineer position. That struck me as unorthodox, so I decided to amuse myself. “Never ascribe to malice that which is adequately explained by incompetence”, someone once said, which should explain both the test and my solution.

#!/usr/bin/php
<?php
 
/*  ArrayWalker (interface)
 
*/
interface ArrayWalker {
    function walk();
    function getElement($y,$x);
}
 
/* FileParser (interface)
 
*/
interface FileParser {
    function toObjectFromFile($fileContentsAsArray);
}
 
/*  SpiralArray:
    Expects 2D array; Walks array in specified pattern,
    and returns elements given a position.
*/
class SpiralArray implements ArrayWalker,FileParser {  
 
    private $twoDimArray;
    private $twoDimArrayOrdered = array();
 
    function __construct() {
 
    }
 
    function __toString() {
        return "SpiralArray";
    }
 
    public function walk() {
        $height = count($this->twoDimArray);
        $width = count($this->twoDimArray[0]);
        $box = $height * $width;
 
        $this->right($height, $width, $box);
 
        return $this;
    }
 
    public function getElement($y /*int*/,$x /*int*/) {
        return $this->twoDimArray[$y][$x];
    }
 
    public function getElementAtPoint($i /*int*/) {
        return $this->twoDimArrayOrdered[$i];
    }
 
    public function toObjectFromFile($fileContentsAsArray) {
        $y = 0;
        $x = 0;
        foreach ($fileContentsAsArray as $line) {
            $line = preg_split("/\s/",$line);
            foreach ($line as $digit) {
                $this->twoDimArray[$y][$x] = $digit;
                $x ++;
            }
            $x = 0;
            $y ++;
        }
        return $this;
    }
 
    public function get() {
        return $this->twoDimArrayOrdered;
    }
 
    private function right ($height,$width,$box) {
        $l = 0;
        $r = $width - 1;
        $t = 0;
        $b = $height - 1;
        $dir = 0; //1,2,3
 
        $i1 = $t;
        $i2 = $l;
 
        for ($i = 0; $i < $box; $i ++ ){
 
            array_push($this->twoDimArrayOrdered, $this->getElement($i1,$i2));
 
             switch($dir) {
             case 0:
                $i2 += 1;
                if ($i2 > $r) { //Going right
                    $i2 -= 1; //Shift back left
                    $t += 1; //Set the top boundary down
                    $i1 = $t;
                    $dir = 1; //Change direction
                }
                break;
            case 1:
                $i1 += 1;
                if ($i1 > $b) { //Going down
                    $i1 -= 1; //Shift back up
                    $r -= 1; //Shift the right boundary left
                    $i2 = $r;
                    $dir = 2;
                }
                break;
            case 2:
                $i2 -= 1;
                if ($i2 < $l) { //Going left
                    $i2 += 1; //Shift back right
                    $b -= 1; //Shift the bottom boundary up
                    $i1 = $b;
                    $dir = 3;
                }
                break;
            case 3:
                $i1 -= 1;
                if ($i1 < $t) { //Going up
                    $i1 += 1; //Shift back down
                    $l += 1; //Shift the left boundary right
                    $i2 = $l;
                    $dir = 0;
                }
                break;
            }
        }
    }
 
    private function left() {
        /* Future Implementation */
    }
 
}
 
/*  FileHandler:
    Wrap some common read operations.
*/
class FileHandler {
 
    /*  readByLine
        Use: FileHandler::readByLine('filePath',true);
    */
    public static function readByLine($file /*Full file path*/,$rtrim /*Boolean*/) { // Return an array of lines
        $lines = array();
        (ISSET($rtrim) && ($rtrim == true)) ? $rtrim = true: $rtrim = false;
        $file_handle = fopen($file, "r");
        while (!feof($file_handle)) {
            $line = fgets($file_handle);
            if ($rtrim) { $line = rtrim($line); }
            array_push($lines,$line);
        }
        fclose($file_handle);
        return $lines;
    }
}
 
$a = new SpiralArray();
print join(" ",$a->toObjectFromFile(FileHandler::readByLine("./q5_input.txt",true))->walk()->get());
 
exit;
?>


 

My input file looks like this:

a b c d e
n o p q f
m t s r g
l k j i h