Koko Eating Bananas

Koko loves to eat bananas. There are n piles of bananas, the ith pile has piles[i] bananas. The guards have gone and will come back in h hours. Koko can decide her banana-eating speed of x bananas per hour. Each hour, she chooses some pile of bananas and eats x bananas from that pile. If Koko doesn't eat all the bananas in a pile, the remaining bananas in that pile are left over and she will not eat them again. Koko likes to keep a consistent eating speed. Given two integer arrays piles and h, where piles[i] is the number of bananas in the ith pile and h is the number of hours that Koko has to eat all the bananas, return the minimum eating speed Koko needs to eat all the bananas within h hours.

int minEatingSpeed(vector<int>& piles, int h) {
  int left = 1, right = *max_element(piles.begin(), piles.end());
  while (left < right) {
    int mid = left + (right - left) / 2;
    int hours = 0;
    for (int pile : piles) {
      hours += (pile + mid - 1) / mid;
    }
    if (hours > h) {
      left = mid + 1;
    }
    else {
      right = mid;
    }
  }
  return left;
}