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#1921 - Eliminate Maximum Number of Monsters

Problem Description

You are playing a video game where you are defending your city from a group of n monsters. You are given a 0-indexed integer array dist of size n, where dist[i] is the initial distance in kilometers of the ith monster from the city.

The monsters walk toward the city at a constant speed. The speed of each monster is given to you in an integer array speed of size n, where speed[i] is the speed of the ith monster in kilometers per minute.

You have a weapon that, once fully charged, can eliminate a single monster. However, the weapon takes one minute to charge. The weapon is fully charged at the very start.

You lose when any monster reaches your city. If a monster reaches the city at the exact moment the weapon is fully charged, it counts as a loss, and the game ends before you can use your weapon.

Return the maximum number of monsters that you can eliminate before you lose, or n if you can eliminate all the monsters before they reach the city.

Solution

/**
 * @param {number[]} dist
 * @param {number[]} speed
 * @return {number}
 */
var eliminateMaximum = function(dist, speed) {
  const n = dist.length;
  const arrivalTimes = new Array(n);

  for (let i = 0; i < n; i++) {
    arrivalTimes[i] = dist[i] / speed[i];
  }

  arrivalTimes.sort((a, b) => a - b);

  for (let i = 0; i < n; i++) {
    if (arrivalTimes[i] <= i) {
      return i;
    }
  }

  return n;
};