#include<bits/stdc++.h>
using namespace std;
namespace IO{
	const int sz=1<<22;
	char a[sz+5],b[sz+5],*p1=a,*p2=a,*t=b,p[205];
	#define gc() (p1==p2?(p2=(p1=a)+fread(a,1,sz,stdin),p1==p2?EOF:*p1++):*p1++)
	#define flush() (fwrite(b,1,t-b,stdout),t=b)
	#define pc(x) (*t++=x,(t-b==sz)?flush():nullptr)
//	#define gc() (getchar())
//	#define flush() (1)
//	#define pc(x) (putchar(x))
	template<class T> inline void read(T &x){
		x=0; char c=gc(),fushu=0;
		while(!isdigit(c)){if(c=='-')fushu=1; c=gc();}
		while(isdigit(c))x=x*10+(c^48),c=gc();
		if(fushu) x=-x;
	}
	inline void read(char &x){
		x=gc();
		while(!isgraph(x))x=gc();
	}
	inline void read(char *x){
		char c=gc();
		while(!isgraph(c))c=gc();
		while(isgraph(c))*x++=c,c=gc();
		*x='\0';
	}
	inline void read(string &x){
		x=""; char c=gc();
		while(!isgraph(c))c=gc();
		while(isgraph(c))x.push_back(c),c=gc();
	}
	template <typename T,typename ...Args> inline void read(T &x,Args &...args) { read(x),read(args...); }
	template<class T> inline void write(T x){
		if(x<0)pc('-'),x=-x;
		if(!x)pc('0');
		int l=0;
		while(x)p[++l]=(x%10)^48,x/=10;
		while(l)pc(p[l--]);
	}
	inline void write(char &x){pc(x);}
	inline void write(const char &x){pc(x);}
	inline void write(char *x){while(*x!='\0')pc(*x++);}
	inline void write(const char *x){while(*x!='\0')pc(*x++);}
	inline void write(string &x){for(auto c:x)pc(c);}
	template <typename T,typename ...Args> inline void write(T x,Args ...args) { write(x),write(args...); }
	struct F{~F(){flush();}}f;
	#undef gc
	#undef flush
	#undef pc
};
using IO::read;
using IO::write;
#define fo(i,l,r) for(int i=(l);i<=(r);++i)
#define fu(i,l,r) for(int i=(l);i<(r);++i)
#define fd(i,r,l) for(int i=(r);i>=(l);--i)
#define ll long long
#define ull unsigned long long
#define ld long double
#define it128 __int128
int T;
int n,m;
const int N=1e6+5;
char a[N<<1];
int b[N],c[N];
int cnt[N];
signed main(){
	read(T);
	while(T--){
		read(n,m);
		read(a+1);
		if(n<m)swap(n,m);
		fo(i,1,n+m){
			cnt[i]=cnt[i-1];
			if(a[i]=='1')cnt[i]++;
		}
		int x=n,y=m;
		fo(i,1,n+m){
			if(!x)c[y--]=a[i]-'0';
			else if(!y)b[x--]=a[i]-'0';
			else if(a[i]=='0'){
				if(x<y)b[x--]=0;
				else c[y--]=0;
			}
			else {
				if(x<y){
					if(cnt[n+m-x+1]-cnt[i]>=y-x+1)b[x--]=1;
					else c[y--]=1;
				}
				else{
					if(cnt[n+m-y+1]-cnt[i]>=x-y+1)c[y--]=1;
					else b[x--]=1;
				}
			}
		}
		b[n+1]=0;
		fo(i,1,m){
			b[i]+=c[i];
		}
		fo(i,1,n)if(b[i]>1)b[i+1]++,b[i]-=2;
		int flag=0;
		fd(i,n+1,1){
			if(b[i]){
				flag=1,write('1');
			}
			else if(flag)write('0');
		}
		if(!flag)write('0');
		write('\n');
	}
	return 0;
}