#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;
}
vi A, B;
int n;
ll solve(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;
}
ll res[N];
ll ans;
ll getans(int t){
t%=n;
if(res[t]==-1)res[t]=solve(t);
ans=max(ans, res[t]);
return res[t];
}
int main(){
//ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n;
string s;
cin>>s;
for(int i=0; i<n+n; i++){
if(s[i]=='B')A.pb(i);
else B.pb(i);
}
ll ans=0;
for(int i=0; i<n; i++){
res[i]=-1ll;
//deb(getans(i));
}
if(n<=5){
for(int i=0;i<n; i++)getans(i);
}
else{
int k=n/8;
for(int i=0; ;i+=k){
if(getans(i)<=getans(i+1) && getans(i+k)>getans(i+k+1)){
int l=i+1, r=i+k;
while(l<r){
int m=(l+r)>>1;
if(getans(m)<=getans(m+1))l=m+1;
else r=m;
}
getans(r);
break;
}
}
}
cout<<ans;
}
Compilation message
monochrome.cpp: In function 'll solve(int)':
monochrome.cpp:40:6: warning: unused variable 'wsk' [-Wunused-variable]
40 | int wsk=n, wsk2=n;
| ^~~
monochrome.cpp:40:13: warning: unused variable 'wsk2' [-Wunused-variable]
40 | int wsk=n, wsk2=n;
| ^~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
340 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Incorrect |
1 ms |
340 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
340 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Incorrect |
1 ms |
340 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
340 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Incorrect |
1 ms |
340 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
340 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Incorrect |
1 ms |
340 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
