Submission #791611

#	Time	Username	Problem	Language	Result	Execution time	Memory
791611		cheat_when_I_was_young	Feast (NOI19_feast)	C++17	30 / 100	26 ms	2696 KiB

feast

// #cheat_when_we_are_young
// #cheatkhitacontre #khionhatoicheat
// #thaycuckythatvong
#include<bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define int long long
using namespace std;
const int NM = 2005, MN = 3e5 + 5;
int n, k, a[MN];
void sub1() {
    for (int i = 1; i <= n; ++i) a[i] += a[i-1];
    cout << a[n];
}
void sub2() {
    int ans = 0;
    for (int i = 1; i <= n; ++i) if (a[i] >= 0) ans += a[i];
    cout << ans;
}
void sub3() {
    int minprefix = 0, ans = 0;
    for (int i = 1; i <= n; ++i) {
        a[i] += a[i-1];
        minprefix = min(minprefix, a[i]);
        ans = max(ans, a[i] - minprefix);
    }
    cout << ans;
}
vector<int> dp_first(NM, 0), dp_second(NM, 0);
void rec(int l, int r, int u, int v) {
    if (l > r) return;
    int mid = (l+r)>>1, ans = INT_MAX, j, tmp;
    for (int i = u; i <= min(v, mid); ++i) {
        tmp = dp_first[i-1] + a[i] - a[mid-1];
        if (ans > tmp) {
            ans = tmp;
            j = i;
        }
    }
    dp_second[mid] = ans;
    rec(l, mid-1, u, j);
    rec(mid+1, r, j, v);
}
void DP() {
    for (int i = 1; i <= n; ++i) dp_first[i] = a[i];
    for (int i = 1; i <= n; ++i) a[i] += a[i-1];
    for (int i = 1; i < k; ++i) {
        rec(1, n, 1, n);
        dp_first = dp_second;
    }
    cout << dp_first[n];
}
signed main() {
	IOS;
    cin >> n >> k;
    int check = 0;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
        if (a[i] < 0) ++check;
    }
    if (check == 0) {
        sub1();
        return 0;
    }
    if (k == 1) {
        sub3();
        return 0;
    }
    if (check == 1) {
        sub2();
        return 0;
    }
    DP();
}

Compilation message (stderr)

feast.cpp: In function 'void rec(long long int, long long int, long long int, long long int)':
feast.cpp:41:8: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
   41 |     rec(l, mid-1, u, j);
      |     ~~~^~~~~~~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 8 / 8
• Subtask 3: 18 / 18
• Subtask 4: 0 / 10
• Subtask 5: 0 / 11
• Subtask 6: 0 / 20
• Subtask 7: 0 / 29