蚂蚁相遇时的掉头等价于穿过。。。明白这一点问题就很简单了
#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
	int len, n, i, t, pos, longest, shortest, temp;
	scanf("%d", &t);
	while( t-- )
	{
		scanf("%d%d", &len, &n);
		for( i=0, longest=0, shortest=0; i<n; i++)
		{
			scanf("%d", &pos);
			temp = max(pos, len-pos);
			longest = max(longest, temp);
			temp = min(pos, len-pos);
			shortest = max(shortest, temp);
		}
		printf("%d %d\n", shortest, longest);
	}
	return 0;
}