一些关于二分的好奇

int l = 1,r = n + 1;
while(l < r)
{
  int mid = (l + r) >> 1;
  if(check(mid)) l = mid + 1;
  else r = mid;
}
l--;

int l = 1,r = n;
while(l < r)
{
	int mid = (l + r) >> 1;
	if(check(mid)) l = mid + 1;
	else r = mid - 1;
}
l--;