HackerRank: 2D Array - DS (Solution)

2D-Array-DS.js

'use strict';

const fs = require('fs');

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', function(inputStdin) {
    inputString += inputStdin;
});

process.stdin.on('end', function() {
    inputString = inputString.split('\n');

    main();
});

function readLine() {
    return inputString[currentLine++];
}

/*
 * Complete the 'hourglassSum' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts 2D_INTEGER_ARRAY arr as parameter.
 */

function hourglassSum(arr) {
    // Number of hourglasses per row (fixed)
    const perRow = 4;
    
    // Number of hourglasses (fixed)
    const total = 16;
    
    // Hourglasses sums array
    const sums = [];
    
    // Loop through each hourglass and calculate its sum
    for (let k = 0; k < total; k++) {
        // The starting index of the hourglass is determined by ceiling 
        // the product of dividing current hourglass index by 
        // `perRow` (4), then limiting the number to (0).
        const i = Math.max(Math.ceil(k / perRow) - 1, 0);
        
        // Loop through each hourglass per row
        for (let j = 0; j < perRow; j++) {
            // Calculate the upper columns ⏳ by slicing from `j` to `j + 3`
            // where `j` is limited to the number of hourglasses per row.
            const upper = arr[i]
                .slice(j, j + 3)
                .reduce((t, v) => t += v, 0);
            
            // Calculate the lower columns ⌛️ by slicing from `j` to `j + 3`
            // where `j` is limited to the number of hourglasses per row.
            // And `i + 2` which points to 2 steps lower at current 
            // row index.
            const lower = arr[i + 2]
                .slice(j, j + 3)
                .reduce((t, v) => t += v, 0);

            // Get the value of the middle column at `i + 1`, and `j + 1`
            const middle = arr[i + 1][j + 1];
            
            // Push the hourglass sum to the array
            sums.push(
                upper + lower + middle
            );
        }
    }
    
    // Return the highest value using a combination of the
    // spread operator and `Math.max(...)` function.
    return Math.max(...sums);
}

function main() {
    const ws = fs.createWriteStream(process.env.OUTPUT_PATH);

    let arr = Array(6);

    for (let i = 0; i < 6; i++) {
        arr[i] = readLine().replace(/\s+$/g, '').split(' ').map(arrTemp => parseInt(arrTemp, 10));
    }

    const result = hourglassSum(arr);

    ws.write(result + '\n');

    ws.end();
}

Function code only:

function hourglassSum(arr) {
    // Number of hourglasses per row (fixed)
    const perRow = 4;
    
    // Number of hourglasses (fixed)
    const total = 16;
    
    // Hourglasses sums array
    const sums = [];
    
    // Loop through each hourglass and calculate its sum
    for (let k = 0; k < total; k++) {
        // The starting index of the hourglass is determined by ceiling 
        // the product of dividing current hourglass index by 
        // `perRow` (4), then limiting the number to (0).
        const i = Math.max(Math.ceil(k / perRow) - 1, 0);
        
        // Loop through each hourglass per row
        for (let j = 0; j < perRow; j++) {
            // Calculate the upper columns ⏳ by slicing the from `j` to `j + 3`
            // where `j` is limited to the number of hourglasses per row.
            const upper = arr[i]
                .slice(j, j + 3)
                .reduce((t, v) => t += v, 0);
            
            // Calculate the lower columns ⌛️ by slicing the from `j` to `j + 3`
            // where `j` is limited to the number of hourglasses per row.
            // And `i + 2` which points to 2 steps lower at current 
            // row index.
            const lower = arr[i + 2]
                .slice(j, j + 3)
                .reduce((t, v) => t += v, 0);

            // Get the value of the middle column at `i + 1`, and `j + 1`
            const middle = arr[i + 1][j + 1];
            
            // Push the hourglass sum to the array
            sums.push(
                upper + lower + middle
            );
        }
    }
    
    // Return the highest value using a combination of the
    // spread operator and `Math.max(...)` function.
    return Math.max(...sums);
}