Submission #370463

#	Time	Username	Problem	Language	Result	Execution time	Memory
370463		Kevin_Zhang_TW	Bigger segments (IZhO19_segments)	C++17	37 / 100	145 ms	60396 KiB

segments

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV 
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T L, T R) { while (L != R) cerr << *L << " \n"[next(L) == R], ++L; }
#else
#define DE(...) 0
#define debug(...) 0
#endif

const int MAX_M = 3010, inf = 1e9, MAX_N = 500010;

int dp[MAX_M][MAX_M], n;

ll a[MAX_N], pf[MAX_N];

ll sum(int l, int r) { return pf[r] - pf[l-1] ; }

void makedp() {
	for (int i = 1;i <= n;++i) {
		dp[i][i] = -inf;

		int P = i;

		for (int j = i-1;j >= 0;--j) {
			dp[i][j] = j == 0 ? 1 : -inf;

			chmin(P, j-1);
			while (P>=0 && sum(j+1, i) >= sum(P+1, j)) --P;

			chmax(dp[i][j], dp[j][P+1] + 1);
			chmax(dp[i][j], dp[i][j+1]);
		}
	}
}

int32_t main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
	cin >> n;

	for (int i = 1;i <= n;++i)
		cin >> a[i], pf[i] = pf[i-1] + a[i];

	auto valid = [&](int l, int r, int i) {
		return pf[i] - pf[r] >= pf[r] - pf[l-1];
	};

	if (n < MAX_N) {
		makedp();
		cout << dp[n][0] << '\n';
		return 0;
	}

	int l = 1, r = 1, k = 0, res = 1;

	for (int i = 2;i <= n;++i) {
		if (valid(l, r, i)) {
			++res;

			while (r + 1 < i) {
				if (!valid(l, r+1, i)) break;
				++r;
				if (k != 0) {
					while (l < r) {
						if (!valid(k, l, r)) break;
						++l;
					}
				}
			}

			k = l;
			l = r+1;
			r = i;
		}
	}

	cout << res << '\n';
}

• Subtask 1: 13 / 13
• Subtask 2: 14 / 14
• Subtask 3: 10 / 10
• Subtask 4: 0 / 36
• Subtask 5: 0 / 27