#include<bits/stdc++.h>
#define For(i,a,b) for (int i=a;i<=b;i++)
using namespace std;
#define int long long

inline int read(){int x=0,f=1;char ch=getchar();for(;ch<'0'||ch>'9';ch=getchar())if(ch=='-')f=-f;for(;ch>='0'&&ch<='9';ch=getchar())x=x*10+ch-'0';return x*f;}
const int N=100005;
struct point{
	int x,i;
}a[N];
int ans[1005][1005];
bool cmp(point a,point b){ return a.x>b.x; }
int ox,oy;
int ex,ey;
int r;

void fill_in_odd(int x,int t){
	while(t>0){
		if(ans[ox][oy]==0)ans[ox][oy]=x,t--;
		ox++;
		if(ox>r){
			oy=oy+2;
			ox=1;
		}
	}
}

void fill_in_even(int x,int t){
	while(t>0){
		ans[ex][ey]=x;
		t--;
		ex-=2;
		if(ex<=0){
			ex=r;
			ey-=2;
		}
		if(ey<=0){
			if(r%2==0){
				ex=r,ey=r-1;
			}else {
				ex=r,ey=r;
			}
		}
	}
}

int b[N],c[N];
int lb,lc;

signed main(){
	
	int T=read();
    For(test,1,T){
        int n,m;
        n=read();m=read();
        for(int i=1;i<=m;i++){
            a[i].x=read();
            a[i].i=i;
        }
        sort(a+1,a+m+1,cmp);
        int now=a[1].x;
        int tmp=n*2/3;
        int las=-1;
        lb=0,lc=0;
        b[++lb]=1;
        for(int i=2;i<=m;i++){
            if(now+a[i].x>=tmp)c[++lc]=las,las=i;
            else now=now+a[i].x,b[++lb]=i;
        }
        r=1;
        while(1){
            int up=(r+1)/2, dw=r/2;
            int now=r*up+up*dw;
            if(now<n){r++;continue;}
            int has=(a[1].x+r-1)/r;
            if(2*has-1>r){r++;continue;}
            break;
            
        }
        if(n==1)r=1;
        ox=1;oy=1;
        if(r%2==0){
            ex=r,ey=r;
        }else {
            ex=r,ey=r-1;
        }
        for(int i=1;i<=r;i++){
            for(int j=1;j<=r;j++){
                ans[i][j]=0;
            }
        }
        fill_in_even(a[las].i,a[las].x);
        for(int i=2;i<=lc;i++){
            int k=c[i];
            fill_in_even(a[k].i,a[k].x);
        }
        for(int i=1;i<=lb;i++){
            int k=b[i];
            fill_in_odd(a[k].i,a[k].x);
        }
        printf("%d\n",r);
        for(int i=1;i<=r;i++){
            for(int j=1;j<=r;j++){
                printf("%d ",ans[i][j]);
            }
            puts("");
        }
    }
    
}
