Submission #709714

#	Time	Username	Problem	Language	Result	Execution time	Memory
709714		Antekb	Monochrome Points (JOI20_monochrome)	C++17	0 / 100	1 ms	340 KiB

monochrome

#include<bits/stdc++.h>

#define st first
#define nd second
#define eb emplace_back
#define pb push_back
#define mp make_pair
#define pp pop_back
#define all(x) x.begin(), x.end()

using namespace std;

using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

void debug(){cerr<<"\n";}
template<typename H, typename... T>
void debug(H h, T... t){cerr<<h;if(sizeof...(t))cerr<<", ";debug(t...);};
#define deb(x...) cerr<<#x<<" = ";debug(x);

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

const int N=1<<19, INF=1e9+5;
int tab[N+N];
void add(int v, int c){
	for(v+=N; v; v>>=1)tab[v]+=c;
}
int sum(int l, int r){
	int ans=0;
	for(l+=N,r+=N; l<r; l>>=1, r>>=1){
		if(l&1)ans+=tab[l++];
		if(r&1)ans+=tab[--r];
	}
	return ans;
}
ll solve(int n, vi A, vi B, int a){
	int wsk=n, wsk2=n;
	vector<pii> V(n);
	for(int i=0; i<a; i++){
		//deb(wsk, wsk2);
		V[i]=mp(A[i], B[n-a+i]);
	}
	for(int i=a; i<n; i++){
		V[i]=mp(A[i], B[i-a]);
	}
	for(pii &i:V)if(i.st>i.nd)swap(i.st, i.nd);
	sort(all(V));
	int ans=0;
	for(int i=0; i<n; i++){
		//deb(V[i]);
		//deb(V[i].st, V[i].nd);
		ans+=sum(V[i].st, V[i].nd);
		add(V[i].nd, 1);
	}
	for(int i=0; i<n; i++){
		add(V[i].nd, -1);
	}
	//deb(ans);
	return ans;
}
int main(){
	//ios_base::sync_with_stdio(0);cin.tie(0);
	int n;
	cin>>n;
	string s;
	cin>>s;
	vi A, B;
	for(int i=0; i<n+n; i++){
		if(s[i]=='B')A.pb(i);
		else B.pb(i);
	}
	ll ans=0;
	int l=0, r=n-1;
	while(l<r){
		int d=(r-l+2)/3;
		//deb(l, r);
		//deb(l+d, r-d);
		ll a1=solve(n, A, B, l+d), a2=solve(n, A, B, r-d);
		ans=max(ans, a1);
		ans=max(ans, a2);
		if(a1>a2)r=r-d-1;
		else l=l+d+1;
	}
	if(l==r)ans=max(ans, solve(n, A, B, l));
	cout<<ans;
}

Compilation message (stderr)

monochrome.cpp: In function 'll solve(int, vi, vi, int)':
monochrome.cpp:38:6: warning: unused variable 'wsk' [-Wunused-variable]
   38 |  int wsk=n, wsk2=n;
      |      ^~~
monochrome.cpp:38:13: warning: unused variable 'wsk2' [-Wunused-variable]
   38 |  int wsk=n, wsk2=n;
      |             ^~~~

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