Project Euler Solutions by Ross Marks

Functions, 001, 002, 003, 004, 005, 006, 007, 008, 009, 010, 011, 012, 013, 014, 015, 016, 017, 018, 019, 020, 021, 022, 023, 024, 025, 026, 027, 028, 029, 030, 031, 032, 033, 034, 035, 036, 037, 038, 039, 040, 041, 042, 043, 044, 045, 046, 047, 048, 049, 050, 051, 052, 053, 054, 055, 056, 057, 058, 059, 060, 061, 062, 063, 064, 065, 066, 067, 068, 069, 070, 071, 072, 073, 074, 075, 076, 077, 078, 079, 080, 081, 082, 083, 084, 085, 086, 087, 088, 089, 090, 091, 092, 093, 094, 095, 096, 097, 098, 099, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520, 521, 522, 523, 524, 525, 526, 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 543, 544, 545, 546, 547, 548, 549, 550, 551, 552, 553, 554, 555, 556, 557, 558, 559, 560,
<?php
/*****************************
 * ProjectEuler - Problem 28
 * By Ross Marks
 *****************************
 * Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:
 * 
 * 21 22 23 24 25
 * 20  7  8  9 10
 * 19  6  1  2 11
 * 18  5  4  3 12
 * 17 16 15 14 13
 * 
 * It can be verified that the sum of the numbers on the diagonals is 101.
 * 
 * What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way?
 ****************************/
define('DOWN', 0);
define('LEFT', 3);
define('RIGHT', 1);
define('UP', 2);

$gridsize = 1001;
$direction = RIGHT;
$total = 0;

$grid = array();
$dimension = $gridsize * $gridsize;
$y = $x = round($gridsize / 2);

/*
$grid[0] = [1,3,6,5,2];
$grid[1] = [1,'',2,'',2];
$grid[2] = [1,'',2,'',2];
$grid[3] = [1,'',2,'',2];
$grid[4] = [1,2,2,2,2];
*/

// create empty grid
for($i = 0; $i < $gridsize; $i++){
  for ($j = 0; $j < $gridsize; $j++){
    $grid[$i][$j] = '';
  }
}

// populate grid
$remain = $distance = 1;
$number = 1;
for ( $count = 0; $count < $dimension; $count++ ){
  $grid[$x][$y] = $number;

  switch ( $direction ){
    case LEFT: $y--; break;
    case UP: $x--; break;
    case DOWN: $x++; break;
    case RIGHT: $y++; break;
  }

  if ( --$remain == 0 ){
    switch ( $direction ){
      case DOWN:
        $direction = LEFT;
        $distance++;

        break;
      case UP:
        $distance++;

      default:
        $direction--;

        break;
    }
    $remain = $distance;
  }
    $number++;
  
}

// work out first diagnol
for($i = 1; $i <= $gridsize; $i++){
  $total = bcadd($total, $grid[$i][$i]);
}
// work out second diagnol
$y = $gridsize;
for($i = 1; $i <= $gridsize; $i++){
  $total = bcadd($total, $grid[$i][$y]);
  $y--;
}
// remove center as added twice
$y = $x = round($gridsize / 2);
$total = bcsub($total, $grid[$y][$x]);

echo "Awnser: $total";

/***
 * Below not used, was for dev
 */

//display
//for($i = 0; $i < $gridsize; $i++){
//  for ($j = 0; $j < $gridsize; $j++){
//    echo " ".$grid[$i][$j]." ";
//  }
//  echo "\n";
//}
//print_r($grid);

//echo (check_grid() ? "true":"false");
/*
function check_grid(){
  global $grid, $gridsize;
  $size = 0;

  // check top
  foreach($grid[1] as $checkme)
    if($checkme)
      $size++;
  // check left
  for($i = 1; $i <= $gridsize; $i++)
    if($grid[$i][1])
      $size++;
  // check bottom
  foreach($grid[$gridsize] as $checkme)
    if($checkme)
      $size++;
  // check right
  for($i = 1; $i <= $gridsize; $i++)
    if($grid[$i][$gridsize-1])
      $size++;
  
  if($size < ($gridsize*3))
    return false;
  return true;
}
*/
?>