Book_Allocation_Problem.cpp

// @author: Abhimanyu Maurya

#include <iostream>
#define ll long long
using namespace std;

//fast i/o
bool ib = ios_base::sync_with_stdio(0);
bool it = cin.tie(0);
bool ot = cout.tie(0);

bool isValid(ll a[], ll n, ll k, ll ans)
{
    ll s = 1, b = 0;
    for (ll i = 0; i < n; i++)
    {
        if (a[i] + b <= ans)
        {
            b += a[i];
        }
        else
        {
            b = a[i];
            s++;
        }
        if (s > k or a[i]>ans)
            return false;
    }
    return true;
}

int main()
{
    ll n, m, a[100001];
    int t;
    cin>>t;
    while (t--)
    {
        cin >> n >> m;
        ll total = 0, res = 0;
        for (ll i = 0; i < n; i++)
        {
            cin >> a[i];
            total += a[i];
        }
        ll start = a[n - 1], end = total;
        while (start <= end)
        {
            ll mid = (start + end) / 2;
            if (isValid(a, n, m, mid))
            {
                res = mid;
                end = mid - 1;
            }
            else
            {
                start = mid + 1;
            }
        }
        cout << res << "\n";
    }
    return 0;
}