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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?

**Credits:**

Special thanks to @pbrother for adding this problem and creating all test cases.

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