#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct Fenwick {
vector<int> a;
int n{};
Fenwick() = default;
Fenwick(int n) : n(n), a(n + 1) {}
int sum(int i) {
int ans = 0;
for (int x = i + 1; x > 0; x -= x & -x) {
ans += a[x];
}
return ans;
}
void modify(int i, int val) {
for (int x = i + 1; x <= n; x += x & -x) {
a[x] += val;
}
}
};
ll intersecting(vector<int> &p) {
int n = p.size();
Fenwick fn(n);
ll ans = 0;
for (int i = 0; i < n; ++i) {
if (p[i] > i) {
ans -= fn.sum(i);
continue;
}
ans += fn.sum(p[i]);
fn.modify(p[i], 1);
}
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
string s;
cin >> s;
vector<int> p(2 * n);
auto check_w = [&](int w) -> bool {
int b = n - w;
int left[2]{w, b}, pos[2]{};
bool yay = true;
for (int i = 0; i < 2 * n; ++i) {
int tp = s[i] == 'B';
if (left[tp]) {
pos[tp] += 1;
--left[tp];
} else {
if (pos[tp ^ 1] == 0 && tp == 1) {
return false;
}
pos[tp ^ 1] -= 1;
}
}
return true;
};
auto check_b = [&](int b) -> bool {
int w = n - b;
int left[2]{w, b}, pos[2]{};
bool yay = true;
for (int i = 0; i < 2 * n; ++i) {
int tp = s[i] == 'B';
if (left[tp]) {
pos[tp] += 1;
--left[tp];
} else {
if (pos[tp ^ 1] == 0 && tp == 0) {
return false;
}
pos[tp ^ 1] -= 1;
}
}
return true;
};
ll ans = 0;
auto calc = [&](int w) -> ll {
int b = n - w;
queue<int> pos[2];
int left[2]{w, b};
bool yay = true;
for (int i = 0; i < 2 * n; ++i) {
int tp = s[i] == 'B';
if (left[tp]) {
pos[tp].push(i);
--left[tp];
} else {
if (pos[tp ^ 1].empty()) {
yay = false;
break;
}
p[i] = pos[tp ^ 1].front();
p[p[i]] = i;
pos[tp ^ 1].pop();
}
}
if (yay) {
ll now = intersecting(p);
ans = max(ans, now);
return now;
} else {
return -1;
}
};
int lo = 0, hi = n + 1;
while (lo + 1 < hi) {
int mid = (lo + hi) >> 1;
if (check_w(mid)) lo = mid;
else hi = mid;
}
int R = lo;
lo = 0, hi = n + 1;
while (lo + 1 < hi) {
int mid = (lo + hi) >> 1;
if (check_b(mid)) lo = mid;
else hi = mid;
}
int L = n - lo;
assert(L <= R);
for (int w = L; w <= R; ++w) {
if (calc(w) == -1) {
cerr << w << " ";
}
}
cerr << endl;
cout << ans << '\n';
return 0;
}
Compilation message
monochrome.cpp: In constructor 'Fenwick::Fenwick(int)':
monochrome.cpp:8:9: warning: 'Fenwick::n' will be initialized after [-Wreorder]
8 | int n{};
| ^
monochrome.cpp:7:17: warning: 'std::vector<int> Fenwick::a' [-Wreorder]
7 | vector<int> a;
| ^
monochrome.cpp:12:5: warning: when initialized here [-Wreorder]
12 | Fenwick(int n) : n(n), a(n + 1) {}
| ^~~~~~~
monochrome.cpp: In lambda function:
monochrome.cpp:59:14: warning: unused variable 'yay' [-Wunused-variable]
59 | bool yay = true;
| ^~~
monochrome.cpp: In lambda function:
monochrome.cpp:79:14: warning: unused variable 'yay' [-Wunused-variable]
79 | bool yay = true;
| ^~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
316 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
320 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
316 KB |
Output is correct |
7 |
Correct |
0 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
316 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
0 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
316 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
320 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
316 KB |
Output is correct |
7 |
Correct |
0 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
316 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
0 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
5 ms |
212 KB |
Output is correct |
15 |
Correct |
4 ms |
212 KB |
Output is correct |
16 |
Correct |
4 ms |
212 KB |
Output is correct |
17 |
Correct |
5 ms |
328 KB |
Output is correct |
18 |
Correct |
2 ms |
212 KB |
Output is correct |
19 |
Correct |
2 ms |
212 KB |
Output is correct |
20 |
Correct |
3 ms |
212 KB |
Output is correct |
21 |
Correct |
3 ms |
316 KB |
Output is correct |
22 |
Correct |
4 ms |
212 KB |
Output is correct |
23 |
Correct |
2 ms |
212 KB |
Output is correct |
24 |
Correct |
2 ms |
212 KB |
Output is correct |
25 |
Correct |
3 ms |
212 KB |
Output is correct |
26 |
Correct |
1 ms |
320 KB |
Output is correct |
27 |
Correct |
1 ms |
316 KB |
Output is correct |
28 |
Correct |
1 ms |
212 KB |
Output is correct |
29 |
Correct |
1 ms |
212 KB |
Output is correct |
30 |
Correct |
1 ms |
212 KB |
Output is correct |
31 |
Correct |
0 ms |
212 KB |
Output is correct |
32 |
Correct |
0 ms |
320 KB |
Output is correct |
33 |
Correct |
4 ms |
340 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
316 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
320 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
316 KB |
Output is correct |
7 |
Correct |
0 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
316 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
0 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
5 ms |
212 KB |
Output is correct |
15 |
Correct |
4 ms |
212 KB |
Output is correct |
16 |
Correct |
4 ms |
212 KB |
Output is correct |
17 |
Correct |
5 ms |
328 KB |
Output is correct |
18 |
Correct |
2 ms |
212 KB |
Output is correct |
19 |
Correct |
2 ms |
212 KB |
Output is correct |
20 |
Correct |
3 ms |
212 KB |
Output is correct |
21 |
Correct |
3 ms |
316 KB |
Output is correct |
22 |
Correct |
4 ms |
212 KB |
Output is correct |
23 |
Correct |
2 ms |
212 KB |
Output is correct |
24 |
Correct |
2 ms |
212 KB |
Output is correct |
25 |
Correct |
3 ms |
212 KB |
Output is correct |
26 |
Correct |
1 ms |
320 KB |
Output is correct |
27 |
Correct |
1 ms |
316 KB |
Output is correct |
28 |
Correct |
1 ms |
212 KB |
Output is correct |
29 |
Correct |
1 ms |
212 KB |
Output is correct |
30 |
Correct |
1 ms |
212 KB |
Output is correct |
31 |
Correct |
0 ms |
212 KB |
Output is correct |
32 |
Correct |
0 ms |
320 KB |
Output is correct |
33 |
Correct |
4 ms |
340 KB |
Output is correct |
34 |
Correct |
196 ms |
340 KB |
Output is correct |
35 |
Correct |
199 ms |
340 KB |
Output is correct |
36 |
Correct |
189 ms |
352 KB |
Output is correct |
37 |
Correct |
178 ms |
448 KB |
Output is correct |
38 |
Correct |
86 ms |
344 KB |
Output is correct |
39 |
Correct |
94 ms |
348 KB |
Output is correct |
40 |
Correct |
124 ms |
340 KB |
Output is correct |
41 |
Correct |
111 ms |
340 KB |
Output is correct |
42 |
Correct |
187 ms |
352 KB |
Output is correct |
43 |
Correct |
72 ms |
352 KB |
Output is correct |
44 |
Correct |
151 ms |
340 KB |
Output is correct |
45 |
Correct |
14 ms |
364 KB |
Output is correct |
46 |
Correct |
13 ms |
340 KB |
Output is correct |
47 |
Correct |
17 ms |
356 KB |
Output is correct |
48 |
Correct |
76 ms |
340 KB |
Output is correct |
49 |
Correct |
56 ms |
340 KB |
Output is correct |
50 |
Correct |
1 ms |
340 KB |
Output is correct |
51 |
Correct |
1 ms |
340 KB |
Output is correct |
52 |
Correct |
162 ms |
340 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
316 KB |
Output is correct |
3 |
Correct |
1 ms |
212 KB |
Output is correct |
4 |
Correct |
0 ms |
320 KB |
Output is correct |
5 |
Correct |
1 ms |
212 KB |
Output is correct |
6 |
Correct |
1 ms |
316 KB |
Output is correct |
7 |
Correct |
0 ms |
212 KB |
Output is correct |
8 |
Correct |
1 ms |
212 KB |
Output is correct |
9 |
Correct |
1 ms |
316 KB |
Output is correct |
10 |
Correct |
1 ms |
212 KB |
Output is correct |
11 |
Correct |
1 ms |
212 KB |
Output is correct |
12 |
Correct |
0 ms |
212 KB |
Output is correct |
13 |
Correct |
0 ms |
212 KB |
Output is correct |
14 |
Correct |
5 ms |
212 KB |
Output is correct |
15 |
Correct |
4 ms |
212 KB |
Output is correct |
16 |
Correct |
4 ms |
212 KB |
Output is correct |
17 |
Correct |
5 ms |
328 KB |
Output is correct |
18 |
Correct |
2 ms |
212 KB |
Output is correct |
19 |
Correct |
2 ms |
212 KB |
Output is correct |
20 |
Correct |
3 ms |
212 KB |
Output is correct |
21 |
Correct |
3 ms |
316 KB |
Output is correct |
22 |
Correct |
4 ms |
212 KB |
Output is correct |
23 |
Correct |
2 ms |
212 KB |
Output is correct |
24 |
Correct |
2 ms |
212 KB |
Output is correct |
25 |
Correct |
3 ms |
212 KB |
Output is correct |
26 |
Correct |
1 ms |
320 KB |
Output is correct |
27 |
Correct |
1 ms |
316 KB |
Output is correct |
28 |
Correct |
1 ms |
212 KB |
Output is correct |
29 |
Correct |
1 ms |
212 KB |
Output is correct |
30 |
Correct |
1 ms |
212 KB |
Output is correct |
31 |
Correct |
0 ms |
212 KB |
Output is correct |
32 |
Correct |
0 ms |
320 KB |
Output is correct |
33 |
Correct |
4 ms |
340 KB |
Output is correct |
34 |
Correct |
196 ms |
340 KB |
Output is correct |
35 |
Correct |
199 ms |
340 KB |
Output is correct |
36 |
Correct |
189 ms |
352 KB |
Output is correct |
37 |
Correct |
178 ms |
448 KB |
Output is correct |
38 |
Correct |
86 ms |
344 KB |
Output is correct |
39 |
Correct |
94 ms |
348 KB |
Output is correct |
40 |
Correct |
124 ms |
340 KB |
Output is correct |
41 |
Correct |
111 ms |
340 KB |
Output is correct |
42 |
Correct |
187 ms |
352 KB |
Output is correct |
43 |
Correct |
72 ms |
352 KB |
Output is correct |
44 |
Correct |
151 ms |
340 KB |
Output is correct |
45 |
Correct |
14 ms |
364 KB |
Output is correct |
46 |
Correct |
13 ms |
340 KB |
Output is correct |
47 |
Correct |
17 ms |
356 KB |
Output is correct |
48 |
Correct |
76 ms |
340 KB |
Output is correct |
49 |
Correct |
56 ms |
340 KB |
Output is correct |
50 |
Correct |
1 ms |
340 KB |
Output is correct |
51 |
Correct |
1 ms |
340 KB |
Output is correct |
52 |
Correct |
162 ms |
340 KB |
Output is correct |
53 |
Execution timed out |
2056 ms |
4184 KB |
Time limit exceeded |
54 |
Halted |
0 ms |
0 KB |
- |