Submission #562477

#	Time	Username	Problem	Language	Result	Execution time	Memory
562477		aryan12	Lamps (JOI19_lamps)	C++17	4 / 100	166 ms	35652 KiB

lamp

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

mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());

int n;
string a, b;

const int N = 1e6 + 5;
int seg[N * 4];

void Build(int l, int r, int pos)
{
	if(l == r)
	{
		seg[pos] = a[l] - '0';
		return;
	}
	int mid = (l + r) >> 1;
	Build(l, mid, pos * 2);
	Build(mid + 1, r, pos * 2 + 1);
	seg[pos] = seg[pos * 2] + seg[pos * 2 + 1];
}

int Query(int l, int r, int pos, int ql, int qr)
{
	if(ql <= l && r <= qr)
	{
		return seg[pos];
	}
	if(ql > r || l > qr)
	{
		return 0;
	}
	int mid = (l + r) >> 1;
	return Query(l, mid, pos * 2, ql, qr) + Query(mid + 1, r, pos * 2 + 1, ql, qr);
}

void Solve() 
{
	cin >> n >> a >> b;
	Build(0, n - 1, 1);
	int prev_value = b[0] - '0', start_pos = 0;
	vector<array<int, 2> > values; // {update, toggle}
	for(int i = 1; i < n; i++)
	{
		if(prev_value != b[i] - '0')
		{
			int ans = Query(0, n - 1, 1, start_pos, i - 1);
			int len = i - 1 - start_pos + 1;
			if((ans == len && prev_value == 1) || (ans == 0 && prev_value == 0)) // no need to "update"
			{
				values.push_back({0, 1}); //0 for set state, 1 (+ 1) for toggle state
			}
			else if((ans == len && prev_value == 0) || (ans == 0 && prev_value == 1)) // no need to toggle
			{
				values.push_back({1, 0});
			}
			else
			{
				values.push_back({1, 1});
			}
			start_pos = i;
			prev_value = b[i] - '0';
		}
	}
	int ans = Query(0, n - 1, 1, start_pos, n - 1);
	int len = n - 1 - start_pos + 1;
	if((ans == len && prev_value == 1) || (ans == 0 && prev_value == 0))
	{
		values.push_back({0, 1});
	}
	else if((ans == len && prev_value == 0) || (ans == 0 && prev_value == 1))
	{
		values.push_back({1, 0});
	}
	else
	{
		values.push_back({1, 1});
	}
	// for(int i = 0; i < values.size(); i++)
	// {
	// 	cout << values[i][0] << " " << values[i][1] << "\n";
	// }
	bool istoggleon = false;
	ans = 0;
	int cnt = 0, cnt1 = 0;
	for(int i = 0; i < values.size(); i++)
	{
		if(values[i][0] == 0 && values[i][1] == 1)
		{
			istoggleon = false;
			// ans += values[i][0] = 0
		}
		else if(values[i][0] == 1 && values[i][1] == 0)
		{
			if(!istoggleon) ans++; // for opening toggle
			istoggleon = true;
			ans = min(ans, ans - cnt + cnt1 / 2 + 1);
			cnt = 0;
			cnt1 = 0;
		}
		else
		{
			ans++;
			// if(istoggleon) ans += values[i][1];
			// else 		  ans += values[i][0];
		}
		if(!istoggleon)
		{
			cnt += values[i][0];
			cnt1++;
		}
	}
	ans = min(ans, ans - cnt + cnt1 / 2 + 2); // if we toggle the last steps
	cout << ans << "\n";
}

int32_t main() 
{
	auto begin = std::chrono::high_resolution_clock::now();
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int t = 1;
	// cin >> t;
	for(int i = 1; i <= t; i++) 
	{
		//cout << "Case #" << i << ": ";
		Solve();
	}
	auto end = std::chrono::high_resolution_clock::now();
    auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
    cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n"; 
	return 0;
}

Compilation message (stderr)

lamp.cpp: In function 'void Solve()':
lamp.cpp:89:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::array<long long int, 2> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   89 |  for(int i = 0; i < values.size(); i++)
      |                 ~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 6
• Subtask 2: 0 / 41
• Subtask 3: 4 / 4
• Subtask 4: 0 / 49