Submission #962371

#	Time	Username	Problem	Language	Result	Execution time	Memory
962371		0npata	Monochrome Points (JOI20_monochrome)	C++17	25 / 100	105 ms	556 KiB

monochrome

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

#define int long long
#define vec vector
#define pi pair<int, int>
#define fst first
#define snd second
#define pb push_back

int n;
string s;
int mes(vec<pi> p) {
	int res = 0;

	int j = p[0].fst;
	int k = p[0].fst;

	int cntw = 1;
	int cntb = 0;

	for(int i = 0; i<n; i++) {
		while(k != p[i].fst) {
			cntw -= s[k]=='W';
			cntb -= s[k] == 'B';
			k+=1;
			k %= 2*n;
		}
		while(j != p[i].snd) {
			j += 1;
			j %= 2*n;
			cntw += s[j]=='W';
			cntb += s[j] == 'B';
		}
		int rw = cntw-1;
		int orb = n-cntb;
		res += min(rw, orb);
	}

	return res;
}

int32_t main() {
	cin >> n;
	cin >> s;

	vec<int> b(0);
	vec<int> w(0);

	for(int i = 0; i<s.size(); i++) {
		if(s[i] == 'W') {
			w.pb(i);
		}
		else {
			b.pb(i);
		}
	}

	int ans = 0;

	const int SQRTN = 600;


	int cand = 0;
	int mx = 0;

	for(int i = 0; i<n; i+=SQRTN) {
		// construct possible pairings
		vec<pi> p;
		for(int j = 0; j<n; j++) {
			p.pb({w[j], b[(j+i)%n]});
		}
		int res = mes(p);

		if(res > mx) cand = i;
	}

	for(int i = max(cand-SQRTN, -n); i<cand; i++) {

		vec<pi> p;
		for(int j = 0; j<n; j++) {
			p.pb({w[j], b[(j+i+n)%n]});
		}

		int res = mes(p);
		ans = max(res, ans);
	}
	for(int i = cand; i<cand+SQRTN; i++) {
		vec<pi> p;
		for(int j = 0; j<n; j++) {
			p.pb({w[j], b[(j+i)%n]});
		}

		int res = mes(p);
		ans = max(res, ans);
	}


	cout << ans << '\n';
}

Compilation message (stderr)

monochrome.cpp: In function 'int32_t main()':
monochrome.cpp:50:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |  for(int i = 0; i<s.size(); i++) {
      |                 ~^~~~~~~~~

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