Submission #746282

#	Time	Username	Problem	Language	Result	Execution time	Memory
746282		baluteshih	Chorus (JOI23_chorus)	C++14	61 / 100	734 ms	196400 KiB

chorus

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define SZ(a) ((int)a.size())
#define ALL(v) v.begin(), v.end()
#define pb push_back

int lft[1000005], lst[1000005];
ll prv[1000005];

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int n, k;
    string s;
    cin >> n >> k >> s;
    if (n > 5000) return 0;

    int cntA = 0, cntB = 0;
    for (int i = 0; i < n + n; ++i) {
        if (s[i] == 'B') ++cntB;
        else lft[++cntA] = cntB;
    }
    for (int i = 1; i <= n; ++i)
        prv[i] = prv[i - 1] + lft[i];
    for (int i = 0; i <= n; ++i)
        lst[lft[i]] = i;
    for (int i = 1; i <= n; ++i)
        lst[i] = max(lst[i], lst[i - 1]);
    for (int i = 0; i <= n; ++i)
        lst[i] = max(i, lst[i]);

    const ll INF = 1e12;
    vector<vector<ll>> dp(k + 1, vector<ll>(n + 1, INF));

    auto line = [&](int i, int q) {
        return pll(-q, dp[i - 1][q] - prv[lst[q]] + q * lst[q]);  
    };

    auto challenge = [&](int i, int x, int y, int z) {
        auto [ax, bx] = line(i, x);
        auto [ay, by] = line(i, y);
        auto [az, bz] = line(i, z);
        return (by - bx) * (ax - az) >= (bz - bx) * (ax - ay);
    };

    auto get_val = [&](int i, int q, int j) {
        auto [a, b] = line(i, q);
        return a * j + b;
    };

    ll fin = INF;
    dp[0][0] = 0;
    for (int i = 1; i <= k; ++i) { 
        deque<int> dq;
        for (int j = 1, p = 0; j <= n; ++j) {
            while (lst[p] <= j && p < j) {
                while (SZ(dq) >= 2 && challenge(i, dq[SZ(dq) - 2], dq.back(), p))
                    dq.pop_back();
                dq.pb(p);
                ++p;
            }
            if (p < j) 
                dp[i][j] = min(dp[i][j], dp[i - 1][p]);
            while (SZ(dq) >= 2 && get_val(i, dq[0], j) >= get_val(i, dq[1], j))
                dq.pop_front();
            if (!dq.empty())
                dp[i][j] = min(dp[i][j], get_val(i, dq[0], j) + prv[j]);
            //for (int q = 0; q < p; ++q)
            //    dp[i][j] = min(dp[i][j], -q * j + (dp[i - 1][q] - prv[lst[q]] + q * lst[q]) + prv[j]);
        }
        fin = min(fin, dp[i][n]);
    }

    cout << fin << "\n";
}

Compilation message (stderr)

chorus.cpp: In lambda function:
chorus.cpp:44:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   44 |         auto [ax, bx] = line(i, x);
      |              ^
chorus.cpp:45:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   45 |         auto [ay, by] = line(i, y);
      |              ^
chorus.cpp:46:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   46 |         auto [az, bz] = line(i, z);
      |              ^
chorus.cpp: In lambda function:
chorus.cpp:51:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   51 |         auto [a, b] = line(i, q);
      |              ^

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