875. Koko Eating Bananas

class Solution {
public:
    int minEatingSpeed(vector<int>& piles, int h) {
        int low = 1;
        int high = *max_element(piles.begin(),piles.end());
        int cnt = 0;
        while(low<high){
            int mid = (low+high)/2; cnt = 0;
            for (auto i : piles) cnt += (i+mid-1)/mid; 
            if (cnt <= h) high = mid; 
            else low = mid+1; 
        }
        return low;
    }
};