Greedy filling

bool check(int k, int N, int W, vector<int> w){
    // multiset<int> st;
    // for(auto x:w){
    //     st.insert(x);
    // }

    vector<int> boxes(k, W);
    vector<int> taken(N, false);

    int box = 0;

    while(box<k){
        bool flag = 0;
        bool flag2 = 1;
        for(int i = N-1;i>=0;i--){
            if(!taken[i] && w[i]<=boxes[box]){
                boxes[box]-=w[i];
                taken[i] = 1;
                flag = 1;
            }
        }

        if(!flag){
            box++;
        }

        for(int i = 0;i<N;i++){
            if(!taken[i]){
            flag2 = false;
        }

        if(flag2){
            break;
        }
    }

    }

    for(int i = 0;i<N;i++){
        if(!taken[i]){
            return false;
        }
    }

    return true;
}

int get_minimum_parcels(int N, int W, vector<int> w) {
    // Write your code here. Complete this function to return the minimum number of parcels required by Michael.
    sort(w.begin(), w.end());

    int l = 1, r = N, ans = N;
    while(l<=r){
        int m = (l+r)/2;
        if(check(m, N, W, w)){
            ans = m;
            r = m - 1;
        }else{
            l = m + 1;
        }
    }
    return ans;
}