Is Subsequence
Given a stringsand a stringt, check ifsis subsequence oft.
You may assume that there is only lower case English letters in bothsandt.tis potentially a very long (length ~= 500,000) string, andsis 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"
Returntrue
.
Example 2:
s="axc"
,t="ahbgdc"
Returnfalse
.
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?
分析
2个指针,一样的时候一起动,否则长动短不动
class Solution:
def isSubsequence(self, s, t):
"""
:type s: str
:type t: str
:rtype: bool
"""
p1=p2=0
n1 = len(s)
n2 = len(t)
if n2<n1:
return False
while p1 < n1 and p2 < n2:
if s[p1] == t[p2]:
p1 +=1
p2 +=1
else:
p2 += 1
if p1 == n1:
return True
return False
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