Submission #341459

#	Time	Username	Problem	Language	Result	Execution time	Memory
341459		ryansee	Monochrome Points (JOI20_monochrome)	C++14	100 / 100	381 ms	410860 KiB

monochrome

#include "bits/stdc++.h"
using namespace std;

#define FAST ios_base::sync_with_stdio(false); cin.tie(0);
#define pb push_back
#define eb emplace_back
#define ins insert
#define f first
#define s second
#define cbr cerr<<"hi\n"
#define mmst(x, v) memset((x), v, sizeof ((x)))
#define siz(x) ll(x.size())
#define all(x) (x).begin(), (x).end()
#define lbd(x,y) (lower_bound(all(x),y)-x.begin())
#define ubd(x,y) (upper_bound(all(x),y)-x.begin())
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());    //can be used by calling rng() or shuffle(A, A+n, rng)
inline long long rand(long long x, long long y) { return rng() % (y+1-x) + x; } //inclusivesss
string inline to_string(char c) {string s(1,c);return s;} template<typename T> inline T gcd(T a,T b){ return a==0?llabs(b):gcd(b%a,a); }

using ll=long long; 
using ld=long double;
#define FOR(i,s,e) for(ll i=s;i<=ll(e);++i)
#define DEC(i,s,e) for(ll i=s;i>=ll(e);--i)
using pi=pair<ll,ll>; using spi=pair<ll,pi>; using dpi=pair<pi,pi>; 

long long LLINF = 1e18;
int INF = 1e9+1e6;
#define MAXN (600006) // put 6
ll n, ans, grad[MAXN], ofs, neg, pos, zero, best;
deque<int> vv[MAXN];
deque<int>*v=vv+(MAXN/2);
deque<char> A;
ll nC2(ll n) { return n * (n-1) / 2; }
int main() {
	FAST
	cin>>n;
	A.resize(n*2);
	for(auto&i:A)cin>>i;
	FOR(i,0,n-1) {
		if(i) grad[i] += grad[i-1];
		if(A[i] == 'W') {
			-- grad[i];
		}
		if(A[n+i] == 'B') {
			++ grad[i];
		}
		ans += abs(grad[i]);
		v[grad[i]].eb(i);
		neg += grad[i] < 0, pos += grad[i] > 0, zero += grad[i] == 0;
	}
	assert(grad[n-1] == 0);
	FOR(i,0,n*2-1) {
		best = max(best, nC2(n) - ans);
		A.eb(A[0]), A.pop_front();
		
		ll o=grad[i]+ofs;
		neg -= grad[i] + ofs < 0, pos -= grad[i] + ofs > 0, zero -= grad[i] + ofs == 0;
		v[grad[i]].pop_front();

		grad[i] += ofs;		
		grad[i] *= -1;
		
		ans += grad[i] * pos, ans -= grad[i] * neg, ans += abs(grad[i]) * zero, ofs += grad[i];
		if(grad[i]==1){
			pos += zero, zero = v[-ofs].size(), neg -= zero;
		}else if(grad[i]==-1){
			neg += zero, zero = v[-ofs].size(), pos -= zero;
		}else assert(grad[i]==0);
		
		grad[i+n] = grad[i+n-1] + o;
		v[grad[i+n]].eb(i+n);
		
		ans -= abs(o), ans += abs(grad[i+n]+ofs);
		neg += grad[i+n] + ofs < 0, pos += grad[i+n] + ofs > 0, zero += grad[i+n] + ofs == 0;
		
		// FOR(j,i+1,i+n) cerr<<grad[j]<<' '; cerr<<'\n';
		// cerr<<ofs<<'\n';
	}
	cout<<best<<'\n';
}

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