Submission #683822

#	Time	Username	Problem	Language	Result	Execution time	Memory
683822		Fysty	Monochrome Points (JOI20_monochrome)	C++17	35 / 100	378 ms	5724 KiB

monochrome

#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define MottoHayaku ios::sync_with_stdio(false);cin.tie(0);
#define rep(i,n) for(int i=0;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define F first
#define S second
#define pb push_back

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const int N=4e5+5;
struct BIT
{
    int a[N];
    void init()
    {
        rep1(i,N-1) a[i]=0;
    }
    void upd(int x,int val)
    {
        for(;x<N;x+=x&-x) a[x]+=val;
    }
    int qry(int x)
    {
        int ret=0;
        for(;x;x-=x&-x) ret+=a[x];
        return ret;
    }
} bit;
int n,to[N];
vector<int> a,b;
string s;
int getans(int i)
{
    i=(i%n+n)%n;
    rep(j,n)
    {
        to[a[j]]=b[(j+i)%n];
        to[b[(j+i)%n]]=a[j];
    }
    bit.init();
    int tot=0;
    rep1(j,n*2)
    {
        if(to[j]<j) bit.upd(j,-1);
        else
        {
            tot+=bit.qry(to[j]);
            bit.upd(to[j],1);
        }
    }
    return tot;
}
signed main()
{
    MottoHayaku
    cin>>n>>s;
    //rep(i,n) s+="BW";
    //shuffle(s.begin(),s.end(),rng);
    //cout<<n<<"\n"<<s<<"\n";
    rep(i,n*2)
    {
        if(s[i]=='B') a.pb(i+1);
        else b.pb(i+1);
    }
    int l=0;
    int r=l+n-1;
    while(l<r)
    {
        int mid=l+r+1>>1;
        int x=getans(mid)-getans(mid-1);
        if(x>0) l=mid;
        else r=mid-1;
    }
    cout<<getans(l)<<"\n";
}

Compilation message (stderr)

monochrome.cpp: In function 'int main()':
monochrome.cpp:76:20: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   76 |         int mid=l+r+1>>1;
      |                 ~~~^~

• Subtask 1: 4 / 4
• Subtask 2: 21 / 21
• Subtask 3: 10 / 10
• Subtask 4: 0 / 65