题目要求找出给定数列中不含重复数字的最长子序列长度。通过记录每个数字第一次出现的位置，利用两个指针更新子序列的起点和长度，最终输出最长子序列的长度。

Two weeks ago as I was reading Software Lead Weekly which I had subscribed to for a while, I discovered its curator, Oren Ellenbogen’s book…