problem
392. Is Subsequence
solution#1: two pointers,快慢指针;
code
solution#2:
Follow Up中描述有很长的字符串,如何优化;
使用 uppper_bound() 来二分查找第一个大于 pre 的位置;
参考
1. leetcode_easy_BS_392. Is Subsequence;
2. Grandyang;
3. uppper_bound;
完