Submission #1053540

#	Time	Username	Problem	Language	Result	Execution time	Memory
1053540		sofijavelkovska	Boarding Passes (BOI22_passes)	C++17	60 / 100	2099 ms	8448 KiB

passes

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

const int MAXN=1e5, MAXK=15;
const long long INF=1e18;

string s;
int n, k;
vector<vector<int> > groups;
double memo[(1<<MAXK)];
double inv[MAXN+1];

double dp(int mask)
{
    if (memo[mask]!=-1)
        return memo[mask];
    if (mask==(1<<k)-1)
        return memo[mask]=0;
    int prefix[n]={0};
    for (int i=0; i<k; i++)
    {
        if (!(mask&(1<<i)))
            continue;
        for (auto x : groups[i])
            prefix[x]=1;
    }
    for (int i=1; i<n; i++)
        prefix[i]=prefix[i-1]+prefix[i];
    int m=prefix[n-1];
    double answer=INF;
    for (int i=0; i<k; i++)
    {
        if (mask&(1<<i))
            continue;
        double mintotal=INF;
        long long maininv=0;
        int g=groups[i].size();
        for (auto x : groups[i])
            if (x!=0)
                maininv=maininv+prefix[x-1];
        mintotal=min(mintotal, inv[g]+maininv);
        for (int j=g-1; j>=0; j--)
        {
            int x=groups[i][j];
            if (x!=0)
                maininv=maininv-prefix[x-1];
            maininv=maininv+(m-prefix[x]);
            mintotal=min(mintotal, inv[j]+inv[g-j]+maininv);
        }
        answer=min(answer, dp(mask|(1<<i))+mintotal);
    }

    return memo[mask]=answer;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> s;
    n=s.size();
    map<char, vector<int> > groupsbychar;
    for (int i=0; i<n; i++)
        groupsbychar[s[i]].push_back(i);
    for (auto t : groupsbychar)
        groups.push_back(t.second);
    k=groups.size();
    for (int i=0; i<=n; i++)
        inv[i]=(double)i*(i-1)/4;
    for (int i=0; i<(1<<k); i++)
        memo[i]=-1;
    cout << fixed << setprecision(5) << dp(0);

    return 0;
}

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