Submission #1627723

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 1000000000
#define mod 1000000007
#define fi first
#define sc second
#define rep(i,x) for(int i=0;i<x;i++)
#define repn(i,x) for(int i=1;i<=x;i++)
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
int n,k;
string s;
string A(int x){ string s="";rep(i,x)s.pb('A');return s;}
string B(int x){ string s="";rep(i,x)s.pb('B');return s;}

string rec(int a,int b,int zan){
    assert(a&&b);
	if(a>1&&b>1){
		if(zan==0) return B(a)+A(b);
		if(zan==1) return A(a-1)+B(b)+A(1);
		if(zan==2) return B(1)+A(a-2)+B(b)+A(1);
		return rec(a-1,b-1,zan-3)+"BA";
	}
	if(a==1&&b==1) return B(1)+A(1);
	if(zan==0) return B(a)+A(b);
	if(a==1){
		if(zan==1) return B(a+b-1)+A(1);
		if(zan==2) return A(a+b-2)+B(1)+A(1);
		if(a+b-3>=1) return rec(1,a+b-3,zan-3)+B(1)+A(1);
		else{ if(zan%2==0) return A(a+b-2)+B(1)+A(1); else return B(a+b-1)+A(1); }
	}
	else{
		if(zan==1) A(a+b-2)+B(1)+A(1);
		if(a+b-3>=1) return rec(1,a+b-3,zan-2)+B(1)+A(1);
		else { if(zan%2==1) return A(a+b-2)+B(1)+A(1); else return B(a+b-1)+A(1); }
	}
}
int main(){
	cin>>n>>k>>s;
	while(1){
		if(k==0){
			cout<<s<<endl; return 0;
		}
		if(s[0]=='A'){
			s[0]='B'; k--; continue;
		}//cout<<"N"<<endl;
		for(int i=0;i<n;){
			while(i<n&&s[i]=='B'){
				if(i!=n-1&&s[i+1]=='A');
				else s[i]='A';
				i++;
			}
			if(i==n){
				k--; continue;
			}
			while(i<n&&s[i]=='A'){
				if(i!=n-1&&s[i+1]=='A') s[i]='B';
				i++;
			}
			if(i==n){//cout<<s<<endl;
				k--; goto out;
			}
		}
	}out:;
	if(k==0){
		cout<<s<<endl; return 0;
	}
	string ans = ""; 
	for(int i=0;i<n;){
		int x = 0,y = 0;
		while(i<n&&s[i]=='B'){
			i++; x++;
		}
		while(i<n&&s[i]=='A'){
			i++; y++;
		}//cout<<x<<y<<endl;
		if(x==0||y==0){cout<<-1<<endl; return 0;}
		ans+=rec(x,y,k);
	}
	cout<<ans<<endl;
}

Submission Info

Judge Result