project-euler-javascript/011.js at master · miloss/project-euler-javascript · GitHub

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// In the 20x20 grid below, four numbers along a diagonal line have been marked
// in red.

var GRID = [
    ['08','02','22','97','38','15','00','40','00','75','04','05','07','78','52','12','50','77','91','08'],
    ['49','49','99','40','17','81','18','57','60','87','17','40','98','43','69','48','04','56','62','00'],
    ['81','49','31','73','55','79','14','29','93','71','40','67','53','88','30','03','49','13','36','65'],
    ['52','70','95','23','04','60','11','42','69','24','68','56','01','32','56','71','37','02','36','91'],
    ['22','31','16','71','51','67','63','89','41','92','36','54','22','40','40','28','66','33','13','80'],
    ['24','47','32','60','99','03','45','02','44','75','33','53','78','36','84','20','35','17','12','50'],
    ['32','98','81','28','64','23','67','10','26','38','40','67','59','54','70','66','18','38','64','70'],
    ['67','26','20','68','02','62','12','20','95','63','94','39','63','08','40','91','66','49','94','21'],
    ['24','55','58','05','66','73','99','26','97','17','78','78','96','83','14','88','34','89','63','72'],
    ['21','36','23','09','75','00','76','44','20','45','35','14','00','61','33','97','34','31','33','95'],
    ['78','17','53','28','22','75','31','67','15','94','03','80','04','62','16','14','09','53','56','92'],
    ['16','39','05','42','96','35','31','47','55','58','88','24','00','17','54','24','36','29','85','57'],
    ['86','56','00','48','35','71','89','07','05','44','44','37','44','60','21','58','51','54','17','58'],
    ['19','80','81','68','05','94','47','69','28','73','92','13','86','52','17','77','04','89','55','40'],
    ['04','52','08','83','97','35','99','16','07','97','57','32','16','26','26','79','33','27','98','66'],
    ['88','36','68','87','57','62','20','72','03','46','33','67','46','55','12','32','63','93','53','69'],
    ['04','42','16','73','38','25','39','11','24','94','72','18','08','46','29','32','40','62','76','36'],
    ['20','69','36','41','72','30','23','88','34','62','99','69','82','67','59','85','74','04','36','16'],
    ['20','73','35','29','78','31','90','01','74','31','49','71','48','86','81','16','23','57','05','54'],
    ['01','70','54','71','83','51','54','69','16','92','33','48','61','43','52','01','89','19','67','48']
];

// The product of these numbers is 26 x 63 x 78 x 14 = 1788696.

// What is the greatest product of four adjacent numbers in the same direction
// (up, down, left, right, or diagonally) in the 20x20 grid?

function product(grid, x, y, dir) {
    var prod = parseInt(grid[x][y]);
    var count = 3;
    while (count--) {
        switch (dir) {
        case 0://Vertical
            x++;
            break;

        case 1://Horizontal
            y++;
            break;

        case 2://Diagonal NW-SE
            x++;
            y++;
            break;

        case 3://Diagonal NE-SW
            x--;
            y++;
            break;
        }
        prod *= parseInt(grid[x][y]);
    }
    return prod;
}

function maxProduct(grid, size) {
    var max = 1;
    for (var i = 0; i < size; i++) {
        for (var j = 0; j < size; j++) {
            if (i < (size - 3)) {
                max = Math.max(max, product(grid, i, j, 0));
            }
            if (j < (size - 3)) {
                max = Math.max(max, product(grid, i, j, 1));
            }
            if (i < (size - 3) && j < (size - 3)) {
                max = Math.max(max, product(grid, i, j, 2));
            }
            if (i > (3 - 1) && j < (size - 3)) {
                max = Math.max(max, product(grid, i, j, 3));
            }
        }
    }
    return max;
}

console.log( maxProduct(GRID, 20) );