Submission #1273738

#	Time	Username	Problem	Language	Result	Execution time	Memory
1273738		thelegendary08	Monochrome Points (JOI20_monochrome)	C++17	35 / 100	2096 ms	17476 KiB

monochrome

#include<bits/stdc++.h>
// #include<atcoder/modint>
#define pb push_back
#define mp make_pair
#define rs resize
#define ft front()
#define bk back()
#define int long long
#define vi vector<int>
#define vvi vector<vector<int>>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define vc vector<char>
#define vb vector<bool>
#define mii map<int,int>
#define f0r(i,n) for(int i=0;i<n;i++)
#define FOR(i,k,n) for(int i=k;i<n;i++)
#define r0f(i,n) for(int i = n-1; i >= 0; i--)
#define R0F(i,k,n) for(int i = n-1; i >= k; i--)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define in(a) int a; cin>>a
#define in2(a,b) int a,b; cin>>a>>b
#define in3(a,b,c) int a,b,c; cin>>a>>b>>c
#define in4(a,b,c,d) int a,b,c,d; cin>>a>>b>>c>>d
#define vin(v,n); vi v(n); f0r(i,n){cin>>v[i];}
#define out(a) cout<<a<<'\n'
#define out2(a,b) cout<<a<<' '<<b<<'\n'
#define out3(a,b,c) cout<<a<<' '<<b<<' '<<c<<'\n'
#define out4(a,b,c,d) cout<<a<<' '<<b<<' '<<c<<' '<<d<<'\n'
#define pout(a) cout<<a.first<<' '<<a.second<<'\n'
#define vout(v) for(auto u : v){cout<<u<<' ';} cout<<endl
#define dout(a) cout<<a<<' '<<#a<<endl
#define dout2(a,b) cout<<a<<' '<<#a<<' '<<b<<' '<<#b<<endl
#define yn(x); if(x){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}
#define p2(x) (1LL << (x))
#define pct(x) (__builtin_popcountll(x))
#define ist(x,y) ((x >> y) & 1)
template<class T, class U> bool ckmin(T& a, const U& b) { return (T)b < a ? a = (T)b, 1 : 0; } 
template<class T, class U> bool ckmax(T& a, const U& b) { return a < (T)b ? a = (T)b, 1 : 0; } 
const int leg = 1e9 + 7;
const int mod = 998244353;
using namespace std;
// using namespace atcoder; 
// using mint = modint998244353;
bool cmp(pii a, pii b){
	if(a.first != b.first)return a.first < b.first; 
	else return a.second > b.second;
}
struct segtree{
	int n; vi tree; 
	segtree(int x){
		n = x; tree.rs(2 * n + 5); 
	}
	void add(int k, int x){
		k += n; tree[k] += x; 
		for(k/=2;k>=1;k/=2)tree[k] = tree[k*2] + tree[k*2+1]; 
	}
	int quer(int l, int r){
		l += n; r += n; int ret = 0; 
		while(l <= r){
			if(l % 2)ret += tree[l++]; 
			if(r % 2 == 0)ret += tree[r--]; 
			l/=2;r/=2;
		}
		// dout2(l,r); dout(ret);
		return ret; 
	}
};
int n;
int solve(vpii v){
	sort(all(v), cmp); 
	// for(auto u : v)pout(u); cout<<'\n';
	segtree S = segtree(2*n); int nst = 0, ans = -n; 
	f0r(i,n){
		nst += S.quer(v[i].second + 1, 2*n-1); 
		S.add(v[i].second, 1); ans += v[i].second - v[i].first; 
	}
	ans -= nst * 2; ans /= 2; return ans; 
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	//ifstream cin(".in");
	//ofstream cout(".out");
	cin>>n; string s; cin>>s; vi a, b; f0r(i, 2*n){if(s[i] == 'W')a.pb(i); else b.pb(i);}
	int ans = 0; 
	f0r(i, n+1){ //pair first i whites with last i blacks, pair first n-i blacks with last n-i whites
		vpii tmp; f0r(j, i)tmp.pb(mp(a[j], b[j + n - i])); f0r(j, n-i)tmp.pb(mp(b[j], a[j+i])); 
		ckmax(ans, solve(tmp)); 	
	}
	out(ans); 
}

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