Submission #898624

#	Time	Username	Problem	Language	Result	Execution time	Memory
898624		AdamGS	Monochrome Points (JOI20_monochrome)	C++17	25 / 100	2060 ms	544 KiB

monochrome

#include<bits/stdc++.h>
using namespace std;
typedef long double ld;
typedef long long ll;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
int main() {
  ios_base::sync_with_stdio(0); cin.tie(0);
  int n;
  string s;
  cin >> n >> s;
  ll b=0, w=n, p=0;
  rep(i, 2*n) {
    if(s[i]=='B') ++b; else --w;
    if(b==w) {
      p=i;
      break;
    }
  }
  ll ans=0;
  for(int p=-1; p<2*n; ++p) {
    vector<pair<int,int>>V;
    int l=2*n-1;
    bool ok=true;
    for(int i=p; i>=0; --i) if(s[i]=='B') {
      while(l>=0 && s[l]=='B') --l;
      if(i>l) {
        ok=false;
        break;
      }
      V.pb({i, l});
      --l;
    }
    if(!ok) continue;
    l=0;
    for(int i=p+1; i<2*n; ++i) if(s[i]=='B') {
      while(l<2*n && s[l]=='B') ++l;
      if(l>i) {
        ok=false;
        break;
      }
      V.pb({l, i});
      ++l;
    }
    if(!ok) continue;
    ll sum=0;
    rep(i, V.size()) rep(j, i) if((V[i].st<V[j].st && V[j].st<V[i].nd && V[i].nd<V[j].nd) 
        || (V[j].st<V[i].st && V[i].st<V[j].nd && V[j].nd<V[i].nd)) {
      ++sum;
    }
    ans=max(ans, sum);
  }
  cout << ans << '\n';
}

Compilation message (stderr)

monochrome.cpp: In function 'int main()':
monochrome.cpp:5:36: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    5 | #define rep(a, b) for(int a = 0; a < (b); ++a)
      |                                    ^
monochrome.cpp:50:5: note: in expansion of macro 'rep'
   50 |     rep(i, V.size()) rep(j, i) if((V[i].st<V[j].st && V[j].st<V[i].nd && V[i].nd<V[j].nd)
      |     ^~~
monochrome.cpp:15:16: warning: variable 'p' set but not used [-Wunused-but-set-variable]
   15 |   ll b=0, w=n, p=0;
      |                ^

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