Submission #788563

#	Time	Username	Problem	Language	Result	Execution time	Memory
788563		someone	Chorus (JOI23_chorus)	C++14	61 / 100	12 ms	1620 KiB

chorus

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

const int N = 5e3 + 42, INF = 1e12 + 42;

vector<int> pre, upd[N];
deque<int> imin, a, b, c;
int n, k, cumul[N], fi[N], dp[N], nbT[N];

int evalCHT(int x) {
    while((int)a.size() >= 2 && (a[0] * x + b[0] > a[1] * x + b[1] || (a[0] * x + b[0] == a[1] * x + b[1] && c[0] >= c[1]))) {
        a.pop_front();
        b.pop_front();
        c.pop_front();
    }
    return a[0] * x + b[0];
}

void pushCHT(int A, int B, int C) {
    int sz = (int)a.size();
    while(sz >= 2 && (B - b[sz-1]) * (a[sz-2] - a[sz-1]) <= (b[sz-1] - b[sz-2]) * (a[sz-1] - A)) {
        sz--;
        a.pop_back();
        b.pop_back();
        c.pop_back();
    }
    a.push_back(A);
    b.push_back(B);
    c.push_back(C);
}

void add(int i) {
    if(fi[i] == i)  {
        pushCHT(-i, dp[i] + i * fi[i] - cumul[fi[i]], nbT[i]);
        return;
    }
    upd[fi[i]].push_back(i);
    while(!imin.empty() && (dp[imin.back()] > dp[i] || (dp[imin.back()] == dp[i] && nbT[imin.back()] > nbT[i])))
        imin.pop_back();
    imin.push_back(i);
}

pair<int, int> solve(int lambda) {
    a.clear();
    b.clear();
    c.clear();
    imin.clear();
    for(int i = 0; i < N; i++)
        upd[i].clear();

    add(0);
    for(int i = 1; i <= n; i++) {
        for(int j : upd[i]) {
            pushCHT(-j, dp[j] + j * fi[j] - cumul[fi[j]], nbT[j]);
            if(!imin.empty() && imin[0] == j)
                imin.pop_front();
        }
        dp[i] = evalCHT(i) + cumul[i];
        nbT[i] = c[0];
        if(!imin.empty())
            if(dp[imin[0]] < dp[i] || (dp[imin[0]] == dp[i] && nbT[imin[0]] < dp[i]))
                nbT[i] = nbT[imin[0]];
        nbT[i]++;
        dp[i] += lambda;
        add(i);
    }
    return {dp[n], nbT[n]};
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int x = 0;
    cin >> n >> k;
    for(int i = 0; i < N; i++)
        fi[i] = N-1;
    pre.clear();
    int nbA = 0;
    for(int i = 0; i < 2*n; i++) {
        char ch; cin >> ch;
        if(ch == 'A') {
            nbA++;
            if(fi[x] == N-1)
                fi[x] = (int)pre.size();
            pre.push_back(x);
        } else {
            x++;
        }
    }
    for(int i = n-1; i > -1; i--)
        if(fi[i] == N-1)
            fi[i] = fi[i+1];
    for(int i = 0; i <= n; i++)
        fi[i] = max(fi[i], i);

    for(int i = 1; i <= n; i++)
        cumul[i] = cumul[i-1] + pre[i-1];

    int deb = 0, fin = INF;
    while(fin - deb > 1) {
        int mid = ((deb + fin) >> 1);
        auto pii = solve(mid-1);
        if(pii.second <= k)
            fin = mid;
        else
            deb = mid;
    }
    cout << solve(deb).first - k * deb << '\n';
}

• Subtask 1: 16 / 16
• Subtask 2: 24 / 24
• Subtask 3: 21 / 21
• Subtask 4: 0 / 26
• Subtask 5: 0 / 13