Codeforces Round 1082 (Div. 2) BC

Codeforces Round 1082 (Div. 2)

B. ABAB Construction

题意简述：定义字符串S奇数位为a偶数位为b，构造T，T初始是空，每次选择S的首位或者尾位的字符，放到T的后面，题目会给出字符串T，询问是否存在这样的S

• 如果n为偶数

#include <bits/stdc++.h>
using namespace std;
void solve(){
	int n;
	cin>>n;
	string s;
	cin>>s;
	int i=0;
	if(n % 2 != 0){
		if(s[0] == 'b'){
			cout<<"NO\n";
			return;
		}
		i++;
	}
	for(;i<n;i+=2){
		if(s[i] == s[i+1] && s[i]!='?'){
			cout<<"NO\n";
			return;
		}
	}
	cout<<"YES\n";
}
int main(){
	
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	int t;cin>>t;
	while(t--){
		solve();
	}
	
	return 0;
}