#include<bits/stdc++.h>
using namespace std;
int n, i, j, k, a, b;
long long ans=0;
char S[400010];
vector<int>A, B;
int seg[1600010];
void init(){for(int i=0;i<8*n;i++)seg[i]=0;}
void update(int id, int s, int e, int x, int v)
{
if(e<x||x<s)return;
if(s==e)
{
seg[id]+=v;
return;
}
int m=s+e>>1;
update(id*2, s, m, x, v);update(id*2+1, m+1, e, x, v);
seg[id]=seg[id*2]+seg[id*2+1];
}
int get(int id, int s, int e, int l, int r)
{
if(e<l||r<s)return 0;
if(l<=s&&e<=r)return seg[id];
int m=s+e>>1;
return get(id*2, s, m, l, r)+get(id*2+1, m+1, e, l, r);
}
void f()
{
init();
vector<pair<int, int> >V;
for(j=i;j<n;j++)V.push_back({A[j-i], B[j]});
for(j=0;j<i;j++)V.push_back({A[j+n-i], B[j]});
for(auto &p:V)if(p.first>p.second)swap(p.first, p.second);
sort(V.begin(), V.end());
long long res=0;
for(auto p:V)
{
int a=p.second;
update(1, 1, 2*n, a, 1);
res+=get(1, 1, 2*n, p.first, a-1);
}
ans=max(ans, res);
}
main()
{
scanf("%d", &n);
scanf("%s", &S);
for(i=0;i<2*n;i++)
{
if(S[i]=='B')A.push_back(i+1);
else B.push_back(i+1);
}
for(i=0;i<n;i++)f(i);
cout<<ans;
}
Compilation message
monochrome.cpp: In function 'void update(int, int, int, int, int)':
monochrome.cpp:17:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
17 | int m=s+e>>1;
| ~^~
monochrome.cpp: In function 'int get(int, int, int, int, int)':
monochrome.cpp:25:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
25 | int m=s+e>>1;
| ~^~
monochrome.cpp: At global scope:
monochrome.cpp:45:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
45 | main()
| ^~~~
monochrome.cpp: In function 'int main()':
monochrome.cpp:48:13: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'char (*)[400010]' [-Wformat=]
48 | scanf("%s", &S);
| ~^ ~~
| | |
| | char (*)[400010]
| char*
monochrome.cpp:54:24: error: too many arguments to function 'void f()'
54 | for(i=0;i<n;i++)f(i);
| ^
monochrome.cpp:28:6: note: declared here
28 | void f()
| ^
monochrome.cpp:47:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
47 | scanf("%d", &n);
| ~~~~~^~~~~~~~~~
monochrome.cpp:48:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
48 | scanf("%s", &S);
| ~~~~~^~~~~~~~~~
