Submission #3425702

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Source Code Expand

// g++ -std=c++11 a.cpp
#include<iostream>
#include<vector>
#include<string>
#include<algorithm>	
#include<map>
#include<set>
#include<unordered_map>
#include<utility>
#include<cmath>
#include<random>
#include<cstring>
#include<queue>
#include<stack>
#include<bitset>
#include<cstdio>
#include<sstream>
#include<iomanip>
#include<assert.h>
#include<typeinfo>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define FOR(i,a) for(auto i:a)
#define pb push_back
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)
#define show1d(v) rep(i,v.size())cout<<" "<<v[i];cout<<endl<<endl;
#define show2d(v) rep(i,v.size()){rep(j,v[i].size())cout<<" "<<v[i][j];cout<<endl;}cout<<endl;
using namespace std;
//kaewasuretyuui
typedef long long ll;
#define int ll
typedef int Def;
typedef pair<Def,Def> pii;
typedef vector<Def> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef pair<Def,pii> pip;
typedef vector<pip>vip;
//#define mt make_tuple
//typedef tuple<int,int,int> tp;
//typedef vector<tp> vt;
template<typename A,typename B>bool cmin(A &a,const B &b){return a>b?(a=b,true):false;}
template<typename A,typename B>bool cmax(A &a,const B &b){return a<b?(a=b,true):false;}
//template<class C>constexpr int size(const C &c){return (int)c.size();}
//template<class T,size_t N> constexpr int size(const T (&xs)[N])noexcept{return (int)N;}
const double PI=acos(-1);
const double EPS=1e-9;
Def inf = sizeof(Def) == sizeof(long long) ? 2e18 : 1e9+10;
int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};
int n;
string s;
string f(int l,int r){
	vvi pos((r-l)/2,vi(2));
	int q;
	q=0;loop(i,l,r)if(s[i]=='a')pos[q++][0]=i;
	q=0;loop(i,l,r)if(s[i]=='b')pos[q++][1]=i;
	string t="";
	if(s[l]=='a'){
		q=-1;
		rep(i,pos.size()){
			if(pos[i][0]>q){
				t+="ab";
				q=pos[i][1];
			}
		}
	}else{
		vi used(r-l);
		rep(i,pos.size()){
			string w="";
			used[pos[pos.size()-1-i][0]-l]=1;
			used[pos[pos.size()-1-i][1]-l]=1;
			rep(j,used.size())if(used[j])w+=s[l+j];
			cmax(t,w);
		}
	}
	return t;
}
signed main(){
	cin>>n>>s;
	vs dp;
	int t=0,p=0;
	rep(i,s.size()){
		if(s[i]=='a')t++;
		else t--;
		if(!t){
			dp.pb(f(p,i+1));
			p=i+1;
		}
	}
	int N=dp.size();
	for(int i=N-1;i>=0;i--){
		string w=dp[i];
		loop(j,i+1,N)cmax(w,dp[i]+dp[j]);
		if(i!=N-1)cmax(w,dp[i+1]);
		dp[i]=w;
	}
	cout<<dp[0]<<endl;
}

Submission Info

Judge Result