Submission #906813

#	Time	Username	Problem	Language	Result	Execution time	Memory
906813		bachhoangxuan	Monochrome Points (JOI20_monochrome)	C++17	100 / 100	1124 ms	15664 KiB

monochrome

// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
- insert(x),erase(x)
- find_by_order(k): return iterator to the k-th smallest element
- order_of_key(x): the number of elements that are strictly smaller
*/

#include<bits/stdc++.h>
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
uniform_real_distribution<> pp(0.0,1.0);
#define int long long
#define ld long double
#define pii pair<int,int>
#define piii pair<int,pii>
#define mpp make_pair
#define fi first
#define se second
const int inf=1e18;
const int mod=998244353;
const int maxn=200005;
const int bl=650;
const int maxs=655;
const int maxm=200005;
const int maxq=1000005;
const int maxl=25;
const int maxa=1000000;
const int root=3;
int power(int a,int n){
    int res=1;
    while(n){
        if(n&1) res=res*a%mod;
        a=a*a%mod;n>>=1;
    }
    return res;
}
const int iroot=power(3,mod-2);
const int base=131;

int bit[2*maxn];

void solve(){
    int n;cin >> n;
    vector<int> b,w;
    for(int i=0;i<2*n;i++){
        char c;cin >> c;
        if(c=='B') b.push_back(i);
        else w.push_back(i);
    }
    auto query = [&](int x){
        if(x<=0) return 0LL;
        int res=0;
        for(int i=x;i>=1;i-=(i&(-i))) res+=bit[i];
        return res;
    };
    auto update = [&](int x){
        for(int i=x;i<=2*n;i+=(i&(-i))) bit[i]++;
    };
    auto cal = [&](int k){
        for(int i=1;i<=2*n;i++) bit[i]=0;
        vector<pii> p;
        for(int i=0;i<n;i++){
            int l=b[i],r=w[(i+k)%n];
            if(l>r) swap(l,r);
            p.push_back({l,r});
        }
        sort(p.begin(),p.end());
        int ans=0;
        for(auto &[l,r]:p){
            ans+=query(r)-query(l-1);
            update(r);
        }
        return ans;
    };
    int l=0,r=n-2,res=0;
    while(l<=r){
        int mid=(l+r)>>1;
        int f1=cal(mid),f2=cal(mid+1);
        res=max({res,f1,f2});
        if(f1<f2) l=mid+1;
        else r=mid-1;
    }
    cout << res << '\n';
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);cout.tie(NULL);
    int test=1;//cin >> test;
    while(test--) solve();
}

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