hourglassSum.js

hourglassSum.js

/*
Sample Input

1 1 1 0 0 0
0 1 0 0 0 0
1 1 1 0 0 0
0 0 2 4 4 0
0 0 0 2 0 0
0 0 1 2 4 0

Sample Output

19

*/
function hourglassSum(arr) {
    const results = []; 
    const hourGlassIndices = [
        [0, 1, 2],
        [null, 1, null],
        [0, 1, 2]
    ];

    const hourGlassPositions = [
        [1, 1, 1, 1],
        [1, 1, 1, 1],
        [1, 1, 1, 1],
        [1, 1, 1, 1]
    ];

    const getHourGlassSum = function(arr, x, y) {
        return hourGlassIndices.reduce((rowSum, row, rowIndex) => {
            let rowValue = row.reduce((colSum, column, columnIndex) => {
                if (hourGlassIndices[rowIndex][columnIndex] !== null) {
                    colSum += arr[rowIndex + y][columnIndex + x];
                }
                return colSum;
            }, 0);
            return rowSum += rowValue;
        }, 0);
    }.bind(null, arr);

    hourGlassPositions.forEach((row, rowIndex) => {
        row.forEach((col, columnIndex) => {
            results.push(getHourGlassSum(columnIndex, rowIndex));
        });
    });

    console.log(results);

    return Math.max.apply(null, results);
}