# # 【LeetCode】392. Is Subsequence 解题报告（Python）

## # 题目描述：

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.
``````

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?

## # 解题方法

``````class Solution(object):
def isSubsequence(self, s, t):
"""
:type s: str
:type t: str
:rtype: bool
"""
queue = collections.deque(s)
for c in t:
if not queue: return True
if c == queue:
queue.popleft()
return not queue
``````

``````class Solution(object):
def isSubsequence(self, s, t):
"""
:type s: str
:type t: str
:rtype: bool
"""
si, ti = 0, 0
while si < len(s) and ti < len(t):
if t[ti] == s[si]:
si += 1
ti += 1
return si == len(s)
``````

## # 日期

2018 年 3 月 15 日 --雾霾消散，春光明媚