제출 #684104

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
684104		vovamr	등산 경로 (IZhO12_route)	C++17	0 / 100	330 ms	65536 KiB

route

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define fi first
#define se second
#define ll long long
#define ld long double
#define sz(x) ((int)(x).size())
#define all(x) 	(x).begin(), (x).end()
#define pb push_back
#define mpp make_pair
#define ve vector
using namespace std;
using namespace __gnu_pbds;
template<class T> using oset = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
const ll inf = 1e18; const int iinf = 1e9;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T> inline bool chmin(T& a, T b) { return (a > b ? a = b, 1 : 0); }
template <typename T> inline bool chmax(T& a, T b) { return (a < b ? a = b, 1 : 0); }

inline void solve() {
	int n, k;
	cin >> n >> k;

	auto get_len = [&n](int l, int r) {
		if (l <= r) return r - l + 1;
		else return n - (l - r) + 1;
	};

	ve<int> a(n);
	for (auto &i : a) cin >> i;

	if (*max_element(all(a)) == *min_element(all(a))) {
		cout << 0;
		return;
	}

	set<array<int,3>> segs;
	{
		int ptr = n;
		while (ptr - 1 >= 0 && a[ptr - 1] == a[0]) --ptr;
		
		int L = (ptr == n ? 0 : ptr);
		for (int i = 0; i < n; ) {
			if (i >= ptr) break;

			int j = i;
			while (j < n && a[j] == a[i]) ++j;

			segs.insert(array<int,3>{j - 1, i == 0 ? L : i, a[i]});
			i = j;
		}
	}

	set<array<int,3>> active;
	for (auto it = segs.begin(); it != segs.end(); ++it) {
		set<array<int,3>>::iterator nxt, prev;
		if (it == --segs.end()) nxt = segs.begin();
		else nxt = it, ++nxt;

		if (it == segs.begin()) prev = --segs.end();
		else prev = it, --prev;

		int vp = (*prev)[2];
		int vn = (*nxt)[2];
		int vc = (*it)[2];

		if (vp > vc && vn > vc) {
			auto &[r, l, x] = *it;
			active.insert( array<int,3>{ get_len(l, r), l, r } );
		}
	}

	ll ans = 0;

	while (k && sz(active)) {
		auto [len, l, r] = *active.begin();
		active.erase(active.begin());

		auto it = segs.lower_bound(array<int,3>{r, l, -iinf});
		set<array<int,3>>::iterator prev, nxt;

		if (it == --segs.end()) nxt = segs.begin();
		else nxt = it, ++nxt;
		if (it == segs.begin()) prev = --segs.end();
		else prev = it, --prev;

		auto [rp, lp, vp] = *prev;
		auto [rn, ln, vn] = *nxt;

		int vc = (*it)[2];

		int can = min(k / len, min(vp, vn) - vc);
		if (!can) break;

		k -= can * len;
		ans += 2 * can;

		segs.erase(array<int,3>{r, l, vc});
		segs.erase(array<int,3>{rn, ln, vn});
		segs.erase(array<int,3>{rp, lp, vp});

		vc += can;
		ve<array<int,3>> nw;
		if (vp != vc) {
			nw.pb({rp, lp, vp});
			if (vc != vn) {
				nw.pb({r, l, vc});
				nw.pb({rn, ln, vn});
			}
			else {
				nw.pb({rn, l, vc});
			}
		}
		else if (vp == vc && vc != vn) {
			nw.pb({r, lp, vc});
			nw.pb({rn, ln, vn});
		}
		else {
			nw.pb({rn, l, vc});
		}

		for (auto &[r, l, x] : nw) {
			segs.insert(array<int,3>{r, l, x});
		}

		for (auto &[r, l, x] : nw) {
			auto it = segs.find({r, l, x});
			set<array<int,3>>::iterator nxt, prev;
			if (it == --segs.end()) nxt = segs.begin();
			else nxt = it, ++nxt;

			if (it == segs.begin()) prev = --segs.end();
			else prev = it, --prev;

			int vp = (*prev)[2];
			int vn = (*nxt)[2];
			int vc = (*it)[2];

			if (vp > vc && vn > vc) {
				auto &[r, l, x] = *it;
				active.insert( array<int,3>{ get_len(l, r), l, r } );
			}
		}
	}

	cout << ans;
}

signed main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	int q = 1; // cin >> q;
	while (q--) solve();
	cerr << fixed << setprecision(3) << "Time execution: " << (double)clock() / CLOCKS_PER_SEC << endl;
}

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