#include<bits/stdc++.h>
#define int long long
using namespace std;

void solve(){
	int n;string s;cin>>n>>s;
	vector<int> x(n),y(n);
	for(int i=0;i<n;i++)x[i]=s[i]-'0';
	vector<int> ans;
	auto op=[&](int i){
		assert(x[i]==0);
		x[i]^=1,x[(i+1)%n]^=1,x[(i-1+n)%n]^=1,y[i]^=1;
		ans.push_back(i);
	};
	for(y[0]=0;y[0]<2;y[0]++)
		for(y[1]=0;y[1]<2;y[1]++){
			for(int i=2;i<n;i++)y[i]=y[i-2]^y[i-1]^x[i-1]^1;
			bool ok=true;
			for(int i=0;i<n;i++){
				int now=x[i]^y[i]^y[(i-1+n)%n]^y[(i+1)%n];
				if(now==0){
					ok=false;
					break;
				}
			}
			if(!ok)continue;
			// cout<<"y ";for(int i=0;i<n;i++)cout<<y[i]<<" \n"[i==n-1];
			for(int t=0;t<100;t++){
				for(int i=0;i<n;i++)if(x[i]==0&&y[i]==1)op(i);
			}
			// cout<<"x ";for(int i=0;i<n;i++)cout<<y[i]<<" \n"[i==n-1];
			// cout<<"y ";for(int i=0;i<n;i++)cout<<y[i]<<" \n"[i==n-1];
			for(int t=0;t<100;t++){
				for(int i=0;i<n;i++)if(x[i]==1&&y[i]==1){
					int l=(i-1+n)%n,r=(i+1)%n;
					if(x[r]==0&&y[r]==0){
						op(r);op(i);op(l);op(r);
					}else if(x[l]==0&&x[l]==0){
						op(l);op(i);op(r);op(l);
					}
				}
			}
			cout<<ans.size()<<endl;
			for(auto x:ans)cout<<x+1<<' ';cout<<endl;
			return;
		}
	cout<<0<<endl;
}

signed main(){
	int t;cin>>t;
	while(t--)solve();
	return 0;
}