#include <bits/stdc++.h>
#define pii pair<int, int>
#define fi first
#define se second
#define MP make_pair
#define ep emplace
#define eb emplace_back
//#define int long long
#define rep(i, j, k) for (int i = j; i <= k; i++)
#define per(i, j, k) for (int i = j; i >= k; i--)
typedef double db;
typedef long double ldb;
typedef long long ll;
typedef __int128 lll;
typedef unsigned long long ull;
typedef unsigned int ui;
using namespace std;

int read() {
	int s = 0, f = 1;
	char c = getchar();
	while (c < '0' || c > '9') f ^= (c == '-'), c = getchar();
	while (c >= '0' && c <= '9') s = s * 10 + c - '0', c = getchar();
	return f ? s : -s;
}

int n,m,s[200005],a[100005],b[100005],pos[200005],id[200005],ans[100005],tot;

signed main() {
	for(int T=read();T--;){
		n=read(),m=read();
		int nn=n,mm=m,top=0;tot=0;
		rep(i,1,n+m)scanf("%1d",&s[i]);
		rep(i,1,max(n,m))a[i]=b[i]=0;
		rep(i,1,n+m)if(s[i])++top,id[pos[top]=i]=top;
		rep(i,1,nn+mm){
			if(!n||!m){
				if(!n)a[m--]=s[i];
				if(!m)a[n--]=s[i];
				continue;
			}
			if(s[i]){
				if(n<m){
					if(pos[id[i]+m-n]&&nn+mm-pos[id[i]+m-n]+m-n>=m)a[n--]=1;
					else b[m--]=1;
				}else{
					if(pos[id[i]+n-m]&&nn+mm-pos[id[i]+n-m]+n-m>=n)b[m--]=1;
					else a[n--]=1;
				}
			}else{
				if(n<m)n--;
				else m--;
			}
		}
		n=nn,m=mm;
		int j=0;
		rep(i,1,max(n,m)){
			ans[++tot]=(a[i]^b[i]^j)&1;
			j=(a[i]+b[i]+j)>>1;
		}
		if(j)ans[++tot]=1;
		bool flag=1;
		per(i,tot,1){
			flag&=!ans[i];
			if(!flag)putchar(ans[i]+'0');
		}
		if(flag)putchar('0');
		putchar('\n');
	}
	return 0;
}