Submission #788455

#	Time	Username	Problem	Language	Result	Execution time	Memory
788455		someone	Chorus (JOI23_chorus)	C++14	16 / 100	3 ms	1224 KiB

chorus

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

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

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

int evalCHT(int x) {
    if(a.empty()) return INF;
    if((int)a.size() == 1)
        return a[0] * x + b[0];
    if(a[0] * x + b[0] > a[1] * x + b[1]) {
        a.pop_front();
        b.pop_front();
    }
    return a[0] * x + b[0];
}

void pushCHT(int A, int B) {
    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();
    }
    a.push_back(A);
    b.push_back(B);
}

void add(int i, int nbG) {
    if(fi[i] == i)  {
        pushCHT(-i, dp[nbG-1][i] + i * fi[i] - cumul[fi[i]]);
        return;
    }
    upd[fi[i]].push_back(i);
    while(!imin.empty() && dp[nbG-1][imin.back()] > dp[nbG-1][i])
        imin.pop_back();
    imin.push_back(i);
}

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;
    for(int i = 0; i < 2*n; i++) {
        char c; cin >> c;
        if(c == 'A') {
            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];
    for(int i = 1; i <= n; i++)
        dp[0][i] = INF;

    for(int nbG = 1; nbG <= k; nbG++) {
        a.clear();
        b.clear();
        imin.clear();
        for(int i = 0; i < N; i++)
            upd[i].clear();

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

    cout << dp[k][n] << '\n';
}

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