392. Is Subsequence
Given a string s and a string t, check if s is subsequence of t. You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100). A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, "ace" is a subsequence of "abcde" while "aec" is not). Example 1: s = "abc", t = "ahbgdc" Return true. Example 2: s = "axc", t = "ahbgdc" Return false. Follow up: If there are lots of incoming S, say S1, S2, ... , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?
follow up question很有意思
class Solution(object): def isSubsequence(self, s, t): """ :type s: str :type t: str :rtype: bool """ if s == '': return True for i in xrange(len(t)): if t[i] == s: return self.isSubsequence(s[1:],t[i+1:]) return False
class Solution(object): def isSubsequence(self, s, t): """ :type s: str :type t: str :rtype: bool """ if s == '': return True ps, pt = 0, 0 while ps < len(s) and pt < len(t): if s[ps] == t[pt]: ps += 1 pt += 1 return ps >= len(s)