Submission #370717

#	Time	Username	Problem	Language	Result	Execution time	Memory
370717		Kevin_Zhang_TW	Bigger segments (IZhO19_segments)	C++17	100 / 100	112 ms	17036 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_N = 500010;
const ll inf = 1ll << 58;
 
int dp[MAX_N], n;
ll lstlen[MAX_N];
 
ll a[MAX_N], pf[MAX_N];

ll getb(int i) { return lstlen[i] + pf[i]; }
 
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];
	};

	deque <int> stk1, stk2;

	dp[1] = 1;
	lstlen[1] = a[1];

	for (int i = 2;i <= n;++i) {
		dp[i] = dp[i-1];
		lstlen[i] = lstlen[i-1] + a[i];

		while (stk2.size()) {
			if (getb(stk2.back()) < getb(i-1)) break;
			stk2.pop_back();
		}
		stk2.pb(i-1);

		if (pf[i] >= getb(stk2[0])) {
			++dp[i];
			lstlen[i] = inf;
			while (stk2.size()) {
				if (pf[i] < getb(stk2[0])) 
					break;
				chmin(lstlen[i], pf[i] - pf[stk2[0]]);
				stk2.pop_front();
			}
			stk1 = stk2;
			deque<int>().swap(stk2);
			continue;
		}

		while (stk1.size()) {
			if (pf[i] < getb(stk1[0]))
				break;
			chmin(lstlen[i], pf[i] - pf[stk1[0]]);
			stk1.pop_front();
		}
	}
	cout << dp[n] << '\n';
}

Compilation message (stderr)

segments.cpp: In function 'int32_t main()':
segments.cpp:35:7: warning: variable 'valid' set but not used [-Wunused-but-set-variable]
   35 |  auto valid = [&](int l, int r, int i) {
      |       ^~~~~

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