Submission #846008

#	Time	Username	Problem	Language	Result	Execution time	Memory
846008		damwuan	Boarding Passes (BOI22_passes)	C++17	55 / 100	77 ms	5780 KiB

passes

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define for1(i,j,k) for(int i=j;i<=k;i++)
#define for2(i,j,k) for(int i=j;i>=k;i--)
#define for3(i,j,k,l) for(int i=j;i<=k;i+=l)
#define bit(n,i) ((n>>i)&1)
#define all(x) x.begin(),x.end()
#pragma GCC optimize("O2,unroll-loops")
#pragma GCC target("avx,avx2,bmi,bmi2,sse,sse2,sse3,ssse3,sse4,popcnt")
//#define int long long
typedef long long ll;
typedef pair<int,int> pii;
typedef double ld;
typedef pair<ld,ld> pdd;
typedef pair<ll,ll> pll;
const ll maxn=1e5+5;
const ll offset=1e9;
const ll block_sz=317;
const ll inf=1e9;
const ll mod=1e9+7;
int n,a[maxn],cost[(1<<15)+2][16],dp[(1<<15)+2],id[16],g=-1,pre[16][maxn],suf[16][maxn];
vector<int> L[16];
string s;
void sol()
{
    cin >> s;
    n=s.size();
    s=' '+s;
    for1(i,0,15) id[i]=-1;
    for1(i,1,n)
    {
        if (id[s[i]-'A']==-1)
        {
            id[s[i]-'A']=++g;
        }
        L[id[s[i]-'A']].pb(i);
        a[i]=id[s[i]-'A'];
        //cerr<< a[i]<<'\n';
    }
    g++;
    for1(i,1,n)
    {
        for1(j,0,g-1)
        {
            pre[j][i]=pre[j][i-1]+((a[i]==j)?1:0);
        }
    }
    for2(i,n,1)
    {
        for1(j,0,g-1)
        {
            suf[j][i]=suf[j][i+1]+((a[i]==j)?1:0);
        }
    }
    for1(i,0,g-1)
    {
        int k1=L[i].size()/2;
        int k2=L[i].size()-k1;
        cost[0][i]=(k1*(k1-1)+k2*(k2-1))/2;
    }
    for1(mask,1,(1<<g)-1)
    {
        for1(i,0,g-1)
        {
            int dem=0,tt=L[i].size();
            if (!((mask>>i)&1))
            {
                for2(k,tt-1,0)
                {
                    for1(j,0,g-1)
                    {
                        if ((mask>>j)&1)
                        {
                            dem+=suf[j][L[i][k]];
                        }
                    }
                }

                cost[mask][i]=dem*2+tt*(tt-1)/2;
//                if (mask==2 && i==0)
//                {
//                    cout <<cost[mask][i]<< " wtf\n";
//                }
                for1(k,0,tt-1)
                {
                    for1(j,0,g-1)
                    {
                        if ((mask>>j)&1)
                        {
                            dem+=pre[j][L[i][k]];
                            dem-=suf[j][L[i][k]];
                        }
                    }
                    cost[mask][i]=min(cost[mask][i],dem*2+(k+1)*k/2 + (tt-k-1)*(tt-k-2)/2);
                }
            }
        }
    }
    //bitset<4> xxx(2);
    //cout << xxx<<'\n';
    //cout << cost[2][0];
    for1(mask,0,(1<<g)-1) dp[mask]=inf;
    dp[0]=0;
    for1(mask,0,(1<<g)-1)
    {
        for1(i,0,g-1)
        {
            if (!((mask>>i)&1))
            {
                dp[mask^(1<<i)]=min(dp[mask^(1<<i)],dp[mask]+cost[mask][i]);
            }
        }
//        dbg(mask);
//        cout<<' '<<dp[mask]<<'\n';
    }
    //cerr<< g<<'\n';
    cout << dp[(1<<g)-1]/2;
    if (dp[(1<<g)-1]&1) cout << ".5";



}


int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
//    freopen("GROUPDIV.inp","r",stdin);
//    freopen("GROUPDIV.out","w",stdout);

    int t=1;//cin >> t;
    while (t--)
    {
        sol();
    }
}
/*

3 1
12345678
?11
*/

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