ArrayDivision.cpp

//Array Division - https://cses.fi/problemset/task/1085

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const int MOD = 1e9 + 7;
const ll INF = 1e18;

void solve() {
    int n, k;
    cin >> n >> k;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }

    auto ok = [&](ll bound) -> bool {
        int cuts = 1;
        ll sum = 0;
        for (int i = 0; i < n; i++) {
            if (sum + a[i] <= bound) {
                sum += a[i];
            } else {
                sum = a[i];
                if (sum > bound) {
                    return false;
                }
                cuts++;
            }
        }
        return cuts <= k;
    };

    ll left = 0, right = INF, ans = INF;
    while (left <= right) {
        ll mid = left + (right - left)/2;
        if (ok(mid)) {
            ans = mid;
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    cout << ans << endl;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int T = 1;
//    cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}