#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("avx2")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e5 + 5;
int a[4*N], nxt[3*N][2];
ll dp[N];
int ord[2*N];
ll solve(int n, int i) {
i = ord[i];
int ptr[2] = {i+n, i+n}, cnt[4] = {0, 0, 0, 0};
// auto next = [&](int& j) {
// j = j+1 < 2*n ? j+1 : j+1-2*n;
// };
// #define next(x) x = x+1 < 2*n ? x+1 : x+1-2*n
ll val = 0;
for (int j = i, c = a[i]; j < i+n; c = a[++j]) {
cnt[c+2] += nxt[ptr[c]][c] - ptr[c];
ptr[c] = nxt[ptr[c]][c] + 1;
val += min(cnt[c+2], cnt[c^1]) + cnt[c]++;
}
return val;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
auto cur_t = clock();
int n; cin >> n;
string s = cin >> s;
for (int i = 0; i < 2*n; i++)
a[i] = a[i+2*n] = s[i] == 'B', ord[i] = i;
nxt[3*n][0] = nxt[3*n][1] = 3*n;
for (int i = 3*n-1; i >= 0; i--) {
nxt[i][0] = nxt[i+1][0], nxt[i][1] = nxt[i+1][1];
nxt[i][a[i]^1] = i;
}
shuffle(ord, ord+n, rng);
ll ans = 0;
int i = 0;
while (clock() - cur_t < 1993)
ans = max(ans, i < n ? solve(n, i++) : 0);
cout << ans << "\n";
}
Compilation message
monochrome.cpp: In function 'int main()':
monochrome.cpp:34:18: error: conversion from 'std::basic_istream<char>' to non-scalar type 'std::string' {aka 'std::__cxx11::basic_string<char>'} requested
34 | string s = cin >> s;
| ~~~~^~~~
