You need to find the minimum number of refueling stops that a car needs to make to cover a distance (target). Stations is an array of tuples [distance, fuel]. 1 distance = 1 fuel.

min-refueling-stops.js

export function minRefuelStops(target, startFuel, stations) {
  if (startFuel >= target) {
    // if we have enough fuel to cover the target
    return 0;
  }

  // we're going to store fuels of reachable stations in a max heap
  const heap = new MaxHeap();
  // max distance that we can cover in the current moment (equals to amount of fuel since 1 mile = 1 fuel)
  let maxDistance = startFuel;
  // number of refueling stops
  let stops = 0;

  for (let i = 0; i < stations.length; ++i) {
    const [dist, fuel] = stations[i];
    if (dist <= maxDistance) {
      // if we can reach this station, add it to the heap
      heap.push(fuel);
      // handle when the last stop is reachable
      while (
        i === stations.length - 1 &&
        heap.isEmpty() > 0 &&
        maxDistance < target
      ) {
        // last stop may be reachable but we still need to understand what is the min number of refueling stops we need
        // so pop fuels out of the heap until we reach the target distance,
        // or until the heap is empty
        maxDistance += heap.pop();
        stops += 1;
      }
    } else {
      // stop is not reachable, pop the most fuel out of the currently reachable stops and increase the max distance
      // decrement i so we can try to reach this stop again
      maxDistance += heap.pop();
      stops += 1;
      i -= 1;
    }
  }

  return stops;
}

// O(n * logn) since heap push is logn, and we do it n times once for each station. Mem O(n) because heap.