Exams - Labyrinth Escape

/* You are given a rectangular field of size NxM, filled with numbers and directions.
 On each cell on the field there will be a direction marked with the letters l, r, u, d.
 On the first row the values are from 1 to M, on the second row – from M+1 to 2*M, on the third row –
 from 2*M +1 to 3*M, on the Nth row – from (N-1)*M to N*M. By given start position, find the path outside
 of the field, or print if you are lost. The method Solve accepts a zero-based array of strings.
 The arguments are as follows: args[0] contains M and N separated by a single space (" "); args[1] contains R and C –
 the start position (the star position is zero-based); args[2] to args[N+2] contain exactly M characters
 (only the letters 'l', 'r', 'u' or 'd'). The output should contain a single string. */

"use strict";

function solve(args) {
    var dimensions = args[0].split(/\s/).filter(Boolean);
    var rows = parseInt(dimensions[0]), cols = parseInt(dimensions[1]);
    var startPosition = args[1].split(/\s/).filter(Boolean);
    var row = parseInt(startPosition[0]), col = parseInt(startPosition[1]);
    var matrix = new Array(rows);
    for (var i = 2; i < args.length; i += 1) {
        matrix[i - 2] = args[i].split('').filter(Boolean);
    }

    function movingToTheNextCell() {
        var cellValue = matrix[row][col];
        matrix[row][col] = undefined;
        switch (cellValue) {
            case 'l':
                row += 0;
                col += -1;
                break;
            case 'r':
                row += 0;
                col += 1;
                break;
            case 'u':
                row += -1;
                col += 0;
                break;
            case 'd':
                row += 1;
                col += 0;
                break;
        }

        return cellValue;
    }

    var sum = 0, countCells = 0;
    do {
        sum += (row * cols) + col + 1;
        if (matrix[row][col]) {
            movingToTheNextCell();
        } else {
            return console.log("lost %d", countCells);
        }
        countCells += 1;
    } while (row >= 0 && row < rows && col >= 0 && col < cols);

    console.log("out %d", sum);
}

solve([
    '3 4',
    '1 3',
    'lrrd',
    'dlll',
    'rddd'
]);

solve([
    '5 8',
    '0 0',
    'rrrrrrrd',
    'rludulrd',
    'durlddud',
    'urrrldud',
    'ulllllll'
]);

solve([
    '5 8',
    '0 0',
    'rrrrrrrd',
    'rludulrd',
    'lurlddud',
    'urrrldud',
    'ulllllll'
]);