Submission #503124

#	Time	Username	Problem	Language	Result	Execution time	Memory
503124		stanislavpolyn	Bigger segments (IZhO19_segments)	C++17	37 / 100	6 ms	460 KiB

segments

#include <bits/stdc++.h>

#define fr(i, a, b) for(int i = (a); i <= (b); ++i)
#define rf(i, a, b) for(int i = (a); i >= (b); --i)
#define fe(x, y) for(auto& x : y)

#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define mt make_tuple

#define all(x) (x).begin(), (x).end()
#define pw(x) (1LL << (x))
#define sz(x) (int)(x).size()

using namespace std;

mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<typename T>
using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define fbo find_by_order
#define ook order_of_key

template<typename T>
bool umn(T& a, T b) { return (a > b ? (a = b, 1) : 0); }
template<typename T>
bool umx(T& a, T b) { return (a < b ? (a = b, 1) : 0); }

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template<typename T>
using ve = vector<T>;

const int N = 3e3 + 5;

int n;
int a[N];
ll pref[N];
int dp[N][N];
pii par[N][N];

int brute1() {
    fr(i, 0, n) {
        fr(j, 0, n) {
            dp[i][j] = -1e9;
        }
    }

    fr(i, 1, n) {
        dp[i][1] = 1;

        rf(j, i, 1) {
            if(dp[i][j] != -1e9) {
                fr(nxt, i + 1, n) {
                    if(pref[nxt] - pref[i] >= pref[i] - pref[j - 1]) {
                        if(umx(dp[nxt][i + 1], dp[i][j] + 1)) {
                            par[nxt][i + 1] = {i, j};
                        }
                    }
                }
                break;
            }
        }
    }

    int mx = 0;
    pii best;
    fr(i, 1, n) {
        fr(j, 1, n) {
            if(umx(mx, dp[i][j])) {
                best = {i, j};
            }
        }
    }
    ve<int> ans;
    while(1) {
        ans.pb(best.fi);
        if(best.se == 1) break;
        best = par[best.fi][best.se];
    }
    reverse(all(ans));
//    cout << "ans: ";
//    fe(x, ans) cout << x << " ";
//    cout << "\n";

    int prev = 0;
    fe(x, ans) {
//        cout << pref[x] - pref[prev] << " ";
        prev = x;
    }
//    cout << "\n";

    return mx;
}

int solve() {
    ve<int> dp(n + 1), cnt(n + 1);
    fr(i, 0, n) dp[i] = -1e9, cnt[i] = -1e9;

    fr(i, 1, n) {
        if(umx(dp[i], 1)) {
            cnt[i] = 1;
        }
        if(umx(dp[i + 1], dp[i])) {
            cnt[i + 1] = cnt[i];
        }
        ll sum = 0;
        fr(j, i + 1, n) {
            sum += a[j];
            if(sum >= pref[i] - pref[dp[i] - 1]) {
                if(umx(dp[j], i + 1)) {
                    cnt[j] = cnt[i] + 1;
                }
                break;
            }
        }
    }
    return *max_element(all(cnt));
}

int main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    ios::sync_with_stdio(0);
    cin.tie(0);
#else
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    ios::sync_with_stdio(0);
    cin.tie(0);
#endif

    cin >> n;

    fr(i, 1, n) {
        cin >> a[i];
//        a[i] = rng() % int(1e6) + 1;
        pref[i] = a[i] + pref[i - 1];
    }
//    fr(i, 1, n) cout << a[i] << " ";
//    cout << "\n";

//    cout << brute1() << "\n";
//    cout << brute2() << "\n";
    cout << solve() << "\n";

    return 0;
}

Compilation message (stderr)

segments.cpp: In function 'int brute1()':
segments.cpp:92:9: warning: variable 'prev' set but not used [-Wunused-but-set-variable]
   92 |     int prev = 0;
      |         ^~~~

• Subtask 1: 13 / 13
• Subtask 2: 14 / 14
• Subtask 3: 10 / 10
• Subtask 4: 0 / 36
• Subtask 5: 0 / 27