C++(g++ 7.5.0) 解法, 执行用时: 1016ms, 内存消耗: 15096K, 提交时间: 2022-09-09 19:56:31

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

typedef long long ll;

void chk(int &x, int y) {
    if (x > y) x = y;
}

struct BIT {
    vector<int> c;
    BIT(int n) : c(n + 1, 1e9) {}

    void ins(int p, int v) {
        for (p++; p; p -= p & -p) chk(c[p], v);
    }
    int query(int p) {
        int s = 1e9;
        for (p++; p < c.size(); p += p & -p) chk(s, c[p]);
        return s;
    }
};

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int n, k, T;
    cin >> n >> k >> T;
    vector<int> c(n);
    for (int &x : c) {
        cin >> x;
    }
    vector<int> p(n), q(n);
    iota(p.begin(), p.end(), 0);
    for (int &x : q) {
        cin >> x, x--;
    }
    vector a(T + 1, vector<int>(n));
    for (int t = 0; t <= T; t++) {
        for (int i = 0; i < n; i++) {
            a[t][i] = c[p[i]];
        }
        vector<int> _p(n);
        for (int i = 0; i < n; i++) {
            _p[i] = q[p[i]];
        }
        swap(p, _p);
    }
    ll ans = -1e13;
    vector<int> perm(T + 1);
    iota(perm.begin(), perm.end(), 0);
    shuffle(perm.begin(), perm.end(), mt19937(time(0)));
    for (int t : perm) {
        vector<ll> s(n + 1);
        for (int i = 0; i < n; i++) {
            s[i + 1] = s[i] + a[t][i];
        }
        auto val = s;
        sort(val.begin(), val.end());
        val.resize(unique(val.begin(), val.end()) - val.begin());
        vector<int> pos(n + 1);
        for (int i = 0; i <= n; i++) {
            pos[i] = lower_bound(val.begin(), val.end(), s[i]) - val.begin();
        }
        auto chk = [&](ll lim) {
            vector<int> f(n + 1), g(n + 1);
            BIT c1(val.size()), c2(val.size());
            c1.ins(pos[0], f[0] = 0), c2.ins(pos[0], g[0] = 0);
            for (int i = 1; i <= n; i++) {
                int j = lower_bound(val.begin(), val.end(), s[i] - lim) - val.begin();
                c1.ins(pos[i], f[i] = c1.query(j) + 1);
                c2.ins(pos[i], g[i] = c2.query(j) - 1);
            }
            return f[n] <= k && -g[n] >= k;
        };
        ll l = ans, r = 1e13;
        if (chk(l)) continue;
        while (l <= r) {
            ll mid = (l + r) / 2;
            chk(mid) ? r = (ans = mid) - 1 : l = mid + 1;
        }
    }
    cout << ans << "\n";
    return 0;
}

C++(clang++ 11.0.1) 解法, 执行用时: 662ms, 内存消耗: 16092K, 提交时间: 2022-09-11 19:41:48

#include <bits/stdc++.h>
const int MaxN = 2e3 + 5;
const int inf = 1e9;
using ll = long long;
std::mt19937 rng(std::chrono::steady_clock::now().time_since_epoch().count());

int n, k, T, f[MaxN], b[MaxN][MaxN]; ll s[MaxN];
int c1[MaxN], c2[MaxN], dp1[MaxN], dp2[MaxN];

bool check(int a[], ll t)
{
	for(int i = 1; i <= n; ++i) s[i] = s[i - 1] + a[i];
	std::vector<ll> V(s + 1, s + n + 1);
	std::sort(V.begin(), V.end());
	auto rk = [&](ll x) { return std::lower_bound(V.begin(), V.end(), x) - V.begin() + 1; };
	
	std::fill(c1 + 1, c1 + n + 1, inf);
	std::fill(c2 + 1, c2 + n + 1, -inf);
	std::fill(dp1 + 1, dp1 + n + 1, inf);
	std::fill(dp2 + 1, dp2 + n + 1, -inf);
	
	for(int i = 1; i <= n; ++i)
	{
		if(s[i] <= t) dp1[i] = dp2[i] = 1;
		for(int x = n - rk(s[i] - t) + 1; x; x -= (x & -x))
		{
			dp1[i] = std::min(dp1[i], c1[x] + 1);
			dp2[i] = std::max(dp2[i], c2[x] + 1);
		}
		
		for(int x = n - rk(s[i]) + 1; x <= n; x += (x & -x))
		{
			c1[x] = std::min(c1[x], dp1[i]);
			c2[x] = std::max(c2[x], dp2[i]);
		}
	}
	
	return (dp1[n] <= k && k <= dp2[n]);
}

int main()
{
	std::cin >> n >> k >> T;
	for(int i = 1; i <= n; ++i) std::cin >> b[0][i];
	for(int i = 1; i <= n; ++i) std::cin >> f[i];
	
	for(int i = 1; i <= T; ++i)
	for(int j = 1; j <= n; ++j) b[i][j] = b[i - 1][f[j]];
	
	std::vector<int> p(T + 1);
	std::iota(p.begin(), p.end(), 0);
	std::shuffle(p.begin(), p.end(), rng);
	
	ll ans = -2e12;
	for(int i : p) if(!check(b[i], ans))
	{
		ll l = ans, r = 2e12;
		while(l <= r)
		{
			ll mid = l + (r - l) / 2;
			if(check(b[i], mid)) ans = mid, r = mid - 1;
			else l = mid + 1;
		}
	}
	
	std::cout << ans << "\n";
	return 0;
}