leetcode_gym/_problems/isSubSequence.md

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layout	title	last_solved	category	leetcode_url	status
page	Is Subsequence	2020-07-08	strings, 2ptr	https://leetcode.com/problems/is-subsequence	Attempted

Problem

Given a string s and a string t, check if s is subsequence of t.

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).

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?


 

Example 1:

Input: s = "abc", t = "ahbgdc"
Output: true
Example 2:

Input: s = "axc", t = "ahbgdc"
Output: false

Solution

Gotchas:

• 2 ptrs on string, have two conditions on while loop

{% highlight python %}

def isSubsequence(s, t):

sp = 0
tp = 0

while sp<len(s) and tp<len(t):

    if s[sp]==t[tp]:
        sp+=1
        tp+=1
        continue
    else:
        tp+=1

# reached end of s
return sp==len(s)

{% endhighlight %}