Submission #672073

#	Time	Username	Problem	Language	Result	Execution time	Memory
672073		LittleCube	Boarding Passes (BOI22_passes)	C++14	30 / 100	460 ms	17232 KiB

passes

#include <bits/stdc++.h>
#define ll long long 
#define pii pair<int, int>
#define pll pair<ll, ll>
#define F first
#define S second
using namespace std;

int N, G;
double pref[15][15][100005], suf[15][15][100005], cost[15][1 << 15], dp[1 << 15];
string s;


bool cmp(int i, int mask, int mid)
{
	double pre = 0, su = 0;
	for(int j = 0; j < G; j++)
		if(mask & (1 << j))
		{	
			pre += pref[i][j][mid];
			su += suf[i][j][mid + 1];
		}
	pre += pref[i][i][mid];
	su += suf[i][i][mid + 1];
	return pre < su;

}


double sum(int i, int mask, int mid)
{
	double res = 0, pre = 0, su = 0;
	for(int j = 0; j < G; j++)
		if(mask & (1 << j))
		{	
			res += pref[i][j][mid] + suf[i][j][mid + 1];
			// pre += pref[i][j][mid];
			// su += suf[i][j][mid + 1];
		}
	// pre += pref[i][i][mid];
	// su += suf[i][i][mid + 1];
	res += pref[i][i][mid] + suf[i][i][mid + 1];
	//	bitset<4> b = mask;
	// cout << (pre < su ? '<' : (pre == su ? '=' : '>')) << res << ' ';
	return res;
}



signed main()
{
	cin >> s;
	N = s.size();
	s = " " + s + " ";
	for(int i = 1; i <= N; i++)
		G = max(G, s[i] - 'A' + 1);
	for(int i = 0; i < G; i++)
	{	
		int acc[15] = {};
		for(int j = 1; j <= N; j++)
		{
			if(s[j] - 'A' == i)
				for(int k = 0; k < G; k++)
					pref[i][k][j] += (i == k ? 0.5 * acc[k] : 1.0 * acc[k]);
			acc[s[j] - 'A']++;
			for(int k = 0; k < G; k++)
				pref[i][k][j] += pref[i][k][j - 1];
		}
	}
	for(int i = 0; i < G; i++)
	{
		int acc[15] = {};
		for(int j = N; j >= 1; j--)
		{
			if(s[j] - 'A' == i)
				for(int k = 0; k < G; k++)
					suf[i][k][j] += (i == k ? 0.5 * acc[k] : 1.0 * acc[k]);
			acc[s[j] - 'A']++;
			for(int k = 0; k < G; k++)
				suf[i][k][j] += suf[i][k][j + 1];
		}
	}
	//for(int i = 0; i < G; i++)
	//	for(int j = 0; j < G; j++)
	//	{
		//	cout << i << " " << j;
		//	for(int k = 0; k <= N; k++)
		//		cout << " " << pref[i][j][k] << " " << suf[i][j][k] << ",";
		//	cout << '\n';
	//	}
	for(int i = 0; i < G; i++)
		for(int mask = 0; mask < (1 << G); mask++)
			if((mask & (1 << i)) == 0)
			{
				cost[i][mask] = 1e10;
				//cout << i << " ";
				int L = 0, R = N;
				while(R - L > 5000)
				{
					int mid = (L + R) / 2;
					if(cmp(i, mask, mid))
						L = mid;
					else R = mid;
				}
				for(int j = L; j <= R; j++)
					cost[i][mask] = min(cost[i][mask], sum(i, mask, j));	
							
				// bitset<4> b = mask;
				// cout << '\n';
			}
	
	for(int mask = 0; mask < (1 << G); mask++)
	{	
		dp[mask] = (mask == 0 ? 0.0 : 1e10);
		for(int i = 0; i < G; i++)
			if(mask & (1 << i))
				dp[mask] = min(dp[mask], dp[mask ^ (1 << i)] + cost[i][mask ^ (1 << i)]);
	}	
	cout << fixed << setprecision(10) << dp[(1 << G) - 1] << '\n';
}

Compilation message (stderr)

passes.cpp: In function 'double sum(int, int, int)':
passes.cpp:32:18: warning: unused variable 'pre' [-Wunused-variable]
   32 |  double res = 0, pre = 0, su = 0;
      |                  ^~~
passes.cpp:32:27: warning: unused variable 'su' [-Wunused-variable]
   32 |  double res = 0, pre = 0, su = 0;
      |                           ^~

• Subtask 1: 5 / 5
• Subtask 2: 25 / 25
• Subtask 3: 0 / 30
• Subtask 4: 0 / 40