Interview

kensho.js

var marked = {};
function markPoint(matrix, x, y) {
   marked[x+","+y] = true;
}
function isPointMarked(matrix, x, y) {
    return marked[x+","+y];
}
function findNeighbors(matrix, x, y) {
    return [-1, 0, 1].map(function (i) {
        return [-1, 0, 1].map(function (j) {
            return [i + x, j + y];
        });
    }).reduce(function (a, x) {
        return a.concat(x);
    }, []).filter(function (p) {
        if (p[0] == x && p[1] == y) {
            return false;
        }
        if (p[x] < 0 || p[x] >= matrix[0].length
            || p[y] < 0 || p[y] >= matrix.length) {
            return false;
        }
        return true;
    });    
}
function extendMarkedPoints(matrix) {
    Object.keys(marked).map(function (p) {
        return p.split(',').map(function (x) {
            return parseInt(x);
        });
    }).forEach(function (p) {
        var neighbors = findNeighbors(matrix, p[0], p[1]);
        var openMoves = neighbors.filter(function (p) {
            return !isPointMarked(p[0], p[1]) && matrix[p[1]][p[0]] == 0;
        });
        openMoves.forEach(function (p) {
            markPoint(p[0], p[1]);
        });
    });
}
function shortestDistance(matrix, sX, sY, eX, eY) {
    markPoint(matrix, sX, sY);
    var steps = 0;
    while (isPointMarked(eX, eY)) {
        extendMarkedPoints(matrix);
        steps += 1;
    }
    return steps;
}