Submission #1307183

#	Time	Username	Problem	Language	Result	Execution time	Memory
1307183		chithanhnguyen	Feast (NOI19_feast)	C++20	100 / 100	89 ms	14516 KiB

feast

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define fi first
#define se second
#define __builtin_popcount __builtin_popcountll
#define all(x) (x).begin(), (x).end()
#define BIT(x, i) (((x) >> (i)) & 1)
#define MASK(x) ((1ll << (x)))

#define debug(a, l, r) for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n';

const int MAXN = 3e5 + 5;
const int INF  = 1e18 + 7;
int n, k, a[MAXN], pref[MAXN];
// int dp[MAXN][MAXN];
pii dp[MAXN][2];

pii check(int x) {
    dp[1][0] = {0, 0};
    dp[1][1] = {a[1] - x, 1};

    for (int i = 2; i <= n; ++i) {
        dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);

        pii cand1 = {dp[i - 1][0].fi + a[i] - x, dp[i - 1][0].se + 1};
        pii cand2 = {dp[i - 1][1].fi + a[i], dp[i - 1][1].se};
        dp[i][1] = max(cand1, cand2);
    }

    return max(dp[n][0], dp[n][1]);
}

signed main() {
    #ifdef NCTHANH
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr); cout.tie(nullptr);

    cin >> n >> k;

    int cntneg = 0;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
        if (a[i] < 0) ++cntneg;
        pref[i] = pref[i - 1] + a[i]; 
    }

    if (cntneg == 0) {
        cout << pref[n];
        return 0;
    }

    if (k == 1) {
        int pre = 0, res = 0;
        for (int i = 1; i <= n; ++i) {
            pre = min(pre, pref[i - 1]);
            res = max(res, pref[i] - pre);
        }

        cout << res;
        return 0;
    }

    if (cntneg == 1) {
        int sum = 0;
        for (int i = 1; i <= n; ++i)
            if (a[i] >= 0) sum += a[i];
        cout << sum;
        return 0;
    }

    // for (int j = 1; j <= k; ++j) {
    //     int mx = -INF;
    //     for (int i = 1; i <= n; ++i) {
    //         dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
    //         mx = max(mx, dp[i - 1][j - 1] - pref[i - 1]);
    //         dp[i][j] = max(dp[i][j], mx + pref[i]);
    //         // for (int pre = i; pre >= 1; --pre) {
    //         //     dp[i][j] = max(dp[i][j], dp[pre - 1][j - 1] + (pref[i] - pref[pre - 1]));
    //         // }
    //     }
    // }

    // cout << dp[n][k];

    int l = 0, r = 1e15 + 5, ans = 0;
    while (l <= r) {
        int mid = (l + r) >> 1ll;
        pii get = check(mid);
        if (get.se >= k) {
            l = mid + 1;
            ans = mid;
        } else r = mid - 1;
    }

    cout << check(ans).fi + k * ans;

    return 0;
}

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