Submission #580053

#	Time	Username	Problem	Language	Result	Execution time	Memory
580053		wdjpng	Boarding Passes (BOI22_passes)	C++17	5 / 100	4 ms	1612 KiB

passes

#include <bits/stdc++.h>

#define int long long
#define double long double
#define rep(i,n) for(int i =0; i<n; i++)
#define all(a) a.begin(),a.end()

using namespace std;


string s;
int n;
double f(int n)
{
    return ((double) n)*((double) (n-1))/4.0;
}

string ord;
vector<double>mem;
vector<vector<int>>pos;
int g;
// cost to add the group gr with all members of that group with and index <= to i boarding on the left
double cost(int bor, int gr, int i)
{
    vector<int>pref;

    double sum = 0;
    int firstr = upper_bound(all(pos[gr]),i) - pos[gr].begin();

    sum+=f(pos[gr].size()-firstr) + f(firstr);

    return sum;
}

double dfs(int bor)
{
    if(mem[bor]>-0.9) return mem[bor];

    int tmp = 0;
    rep(i,g) if((1<<i)&bor) tmp++;
    if(tmp==1) return f(n/2) + f((n+1)/2);

    double sol = 1e18;
    rep(i,g)
    {
        if(!((1<<i)&bor)) continue;
        int nbor = bor^(1<<i);
        int start = 0, end = n;
        while (end-start>1)
        {
            int c = (start+end)/2;
            if(cost(nbor,i,c)>cost(nbor,i,c+1)) start=c;
            else end=c;
        }
        sol=min(sol, cost(nbor,i,start));
    }
    return mem[bor] = sol;
}
signed main()
{
    cin>>s;
    s.size();
    n=s.size();

    double sum = f(n/2) + f((n+1)/2);
    cout.precision(300);
    
    char maxx=0;
    rep(i,n) maxx=max(maxx, s[i]);
    g='A'-maxx+1;

    pos.resize(g);
    mem.assign(1<<g,-1.0);
    rep(i,n) pos[(s[i]-'A')].push_back(i);

    cout<<dfs((1<<g)-1)<<'\n';
}

Compilation message (stderr)

passes.cpp: In function 'int main()':
passes.cpp:65:12: warning: unused variable 'sum' [-Wunused-variable]
   65 |     double sum = f(n/2) + f((n+1)/2);
      |            ^~~

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