Submission #963071

#	Time	Username	Problem	Language	Result	Execution time	Memory
963071		RaresFelix	Chorus (JOI23_chorus)	C++17	100 / 100	1045 ms	99460 KiB

chorus

#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("avx,avx2,fma")

#define sz(x) int((x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

using namespace std;
using ll = long long;
using ld = long double;  // or double, if TL is tight
using str = string; 
using ii = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vector<int>;
using vll = vector<ll>;

const ll INF = 1e18;

struct CHT {
    int p = 0;
    vector<tuple<ll, ll, int> > V;
    void insert(ll a, ll b, int cnt) { /// ax + b
        //a va scadea mereu
        while(V.size() > 1) {
            auto [a1, b1, c1] = V.end()[-1];
            auto [a2, b2, c2] = V.end()[-2];
            if((b2 - b) * (a1 - a2) <= (b2 - b1) * (a - a2)) {
                V.pop_back();
                p = min(p, int(V.size()) - 1);
            }
            else break;
        }
        V.push_back({a, b, cnt});
    }

    pair<ll, int> query(ll x) {
        if(V.empty()) return {INF, 0};
        ll re = INF;
        auto eval = [&](int i) -> ll {
            return get<0>(V[i]) * x + get<1>(V[i]);
        };
        while(p + 1 < V.size() && eval(p + 1) < eval(p)) ++p;
        return make_pair(eval(p), get<2>(V[p]));
    }
};

int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(0);

    int n, k;
    cin >> n >> k;

    string s0, s;
    cin >> s0;
    ll re0 = 0;
    int nrB = 0, sum = 0;
    for(auto it : s0) {
        if(it == 'A') {
            ++sum;
            s += 'A';
            re0 += nrB;
            if(nrB && sum) {
                s += 'B';
                --nrB;
                --sum;
            }
        } else {
            if(sum) {
                s += 'B';
                --sum;
            } else {
                ++nrB;
            }
        }
    }

    vll A, P(n + 1);
    vll SA;
    P[0] = -1;
    for(auto it : s) {
        if(it == 'A'){
            A.push_back(nrB);
            if(SA.empty())
                SA.push_back(A.back());
            else
                SA.push_back(A.back() + SA.back());
        } 
        else {
            ++nrB;
            P[nrB] = (int)A.size() - 1;
        }
    }
    vll SAP(n);
    for(int i = 0; i < n; ++i) {
        SAP[i] = 0;
        if(P[i] != -1) SAP[i] = SA[P[i]];
    }

    auto cost = [&](ll st, ll dr) {
        return st * P[st] - SAP[st] + SA[dr] - st * dr;
    };


    auto t = [&](ll lambda) {
        ll re = - lambda * k;
        vll DP(n, INF);
        vi Nr(n, 0);

        CHT Sol;

        for(int i = 0; i < n; ++i) {
            DP[i] = cost(0, i) + lambda;
            Nr[i] = 1;
            if(i)
                Sol.insert(-i, i * P[i] - SAP[i] + DP[i - 1], Nr[i - 1]);
            auto [val, nr] = Sol.query(i);
            val += lambda + SA[i];
            if(val < DP[i]) {
                DP[i] = val;
                Nr[i] = nr + 1;
            }
        }
        return make_pair(DP[n - 1] + re, Nr[n - 1] - k);
    };

    ll st = 0, dr = 1e12, mij;

    ll re = 0;
    for(int i = 0; i <= 200; ++i) {
        mij = (st + dr) / 2;
        auto [val, g] = t(mij);
        re = max(re, val);
        if(st == dr) break;
        if(g > 0) st = mij + 1;
        else dr = mij;
    }

    cout << re0 + re << "\n";
    return 0;
}

Compilation message (stderr)

chorus.cpp: In member function 'std::pair<long long int, int> CHT::query(ll)':
chorus.cpp:43:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::tuple<long long int, long long int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |         while(p + 1 < V.size() && eval(p + 1) < eval(p)) ++p;
      |               ~~~~~~^~~~~~~~~~
chorus.cpp:39:12: warning: unused variable 're' [-Wunused-variable]
   39 |         ll re = INF;
      |            ^~

• Subtask 1: 16 / 16
• Subtask 2: 24 / 24
• Subtask 3: 21 / 21
• Subtask 4: 26 / 26
• Subtask 5: 13 / 13