枚举子集还有优化的空间吗？

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define F(i,k,n) for (int i=k;i<=n;i++)
typedef long long ll;
const int N=24;
int n,m,k;
int x[N],y[N],a[N];
int pre[]={1,4,16,64,256,1024,4096,16384,65536
,262144,1048576,4194304,16777216};
int dp[1<<N];
int to[N];
int dx[]={0,0,0,1,-1};
int dy[]={0,1,-1,0,0};
int get_1(int a){
	int sum=0;
	for (int i=a;i;i=i&(i-1)) sum++;
	return sum;
}
bool pan(int a){
	int tot=0;
	F(i,0,k-1){
		if ((a>>i)&1){
			tot++;
			to[tot]=i;
		}
	}
	if (tot==1) return 1;
	F(i,1,tot){
		F(j,0,4){
			int l=x[i]+dx[j],r=y[i]+dy[j];
			bool flag=1;
			F(p,1,tot){
				if (abs(x[to[p]]-l)+abs(y[to[p]]-r)>1) flag=0;
			}
			if (flag) return 1;
		}
	}
	return 0;
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin>>n>>m>>k;
	F(i,0,k-1) cin>>x[i]>>y[i]>>a[i];
	int op=0;
	F(i,0,k-1) op+=pre[i]*a[i];
	memset(dp,0x3f,sizeof dp);
	dp[0]=0;
	F(s,1,op){
		int q=s,flag=0;
		for (int i=k-1;i>=0;i--){
			if (q/pre[i]>a[i]) flag=1;
			q%=pre[i];
		}
		if (flag) continue;
		int change=0,d=s;
		for (int i=k-1;i>=0;i--){
			if (d>=pre[i]) change+=(1<<i);
			while (d>=pre[i]) d-=pre[i];
		}
		for (int j=change;j>=0;j=(j-1)&change){
			if (pan(j)){
				int l=0;
				F(i,0,k-1) if ((j>>i)&1) l+=pre[i];
				dp[s]=min(dp[s],dp[s-l]+1);
			}
			if (!j) break;
		}
	}
	cout<<dp[op];
	return 0;
}