Educational Codeforces Round 150 (Rated for Div. 2) B. Keep it Beautiful

#include <iostream>
#include <cstring>
using namespace std;
const int N=2e5+10;
int a[N],res[N];
int t;
int main(){
	cin>>t;
	while(t--){
		int n;
		cin>>n;
		for(int i=0;i<n;i++){
			cin>>a[i];
		}
		int k=a[0];
		res[0]=1;
		int u=-1;
		for(int i=1;i<n;i++){
			if(u==-1&&k<=a[i]){//前面一段递增序列 
				res[i]=1;
				k=a[i];
			}
			else if(u==-1&&a[i]<=a[0]){//遇到第一个比开头小的数可作为尾巴 
				res[i]=1;
				u=a[i];
			}
			else if(u<=a[i]&&a[i]<=a[0]){//求第二端递增序列所有数字均小于开头 
				res[i]=1;
				u=a[i];
			}
			else res[i]=0;
		}
		for(int i=0;i<n;i++) cout<<res[i];
		cout<<endl;
	}
}