字典序從小到大

#include<cstdio>
#include<algorithm>
using namespace std;
bool vis[30];
int n,r,arr[30],a[30],had;

bool check(int now)
{
	for(int i=now-1;i>=1 && a[i]==a[now];i--)
		if(!vis[i]) return 0;
	return 1;
}

void dfs(int now)
{
	if(now == 0){ for(int i=1;i<=had;i++) printf("%d ",arr[i]);return void(had ? puts("") : had); }
	dfs(now-1);
	if(check(now))
	{
		vis[now] = 1;
		arr[++had] = a[now];
		dfs(now-1);
		vis[now] = 0;
		had--;
	}
}

int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]);
	sort(a+1,a+1+n);
	dfs(n);
}