your "true" PIN is a static value calculated from your card number and a key,
No heap allocations of size, 1, 2, and 4, and none of the garbage that
，推荐阅读服务器推荐获取更多信息
Randomly selecting border points or using simple geometric divisions (squares/hexagons) results in too many border points per cluster (50-80). This leads to a shortcut explosion (N*(N-1)/2 shortcuts), making the files large and and calculations slow.
// ⚠️ 易错点1：长度≤1的数组本身有序，返回0而非n
Kevin Church/BBC News