DAZN Challenge Question 12

dazn_challenge_question_12.js

function widestGap(n, start, finish) {
    // Write your code here
    let gaps = []
    let positionsWithCars = []
    let positionsWithoutCars = []

    const getCarPositions = (start, end, step) => {
      // returns all the positions a car occupies
      //  there's a bug when a car occupies positions such as [2,2], this is solved with a temporary solution:
      //    if (carPositions[1] == undefined) carPositions[1] = car.finish;
      const length = Math.floor(Math.abs((end - start) / step)) + 1;
      return Array.from(Array(length), (x, index) => start + index * step);
    }

    // looping each position on the grid
    for (let position = 0; position <= n; position++) {
      // looping the cars
      for (let startIndex = 0; startIndex < start.length; startIndex++) {
        // creating a car reference
        let car = { start: start[startIndex], finish: finish[startIndex] };

        let carPositions = getCarPositions(car.start, car.finish, 1)

        // fixing bug for cars that are only one position wide
        if (carPositions[1] == undefined) carPositions[1] = car.finish;

        // checking if the current position has a car
        if (carPositions[0] <= position && position <= carPositions[1]) positionsWithCars.push(position)
      }

      // pushing the positions without cars
      if (!positionsWithCars.includes(position)) positionsWithoutCars.push(position)
    }

    // reducing the positions without cars to create arrays of sequential positions
    const result = positionsWithoutCars.reduce((accumulator, currentValue) => {
      // getting the last inner array
      const lastSubArray = accumulator[accumulator.length - 1];

      // checking if the last inner array's last item is different than the last value
      if(!lastSubArray || lastSubArray[lastSubArray.length - 1] !== currentValue - 1) {
        // if so, we create a new array
        accumulator.push([]);
      }

      // adding the value to the array (if we pushed a new one, this is the first value there)
      accumulator[accumulator.length - 1].push(currentValue);

      // returning the accumulator (the array of inner arrays)
      return accumulator;
    }, []);

    // getting all the array lengths
    let arrayLengths = result.map(function(innerArray){return innerArray.length;});

    // returning the biggest array length
    return Math.max(...arrayLengths)
}


// testing the implementation
const result = widestGap(10, [2, 3, 8], [2, 4, 9]);
console.log(result)