# Is Subsequence

## Problem

Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., “ace” is a subsequence of “abcde” while “aec” is not).

Example 1:

```
Input: s = "abc", t = "ahbgdc"
Output: true
```

Example 2:

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

Constraints:

- 0 <= s.length <= 100
- 0 <= t.length <= 104
- s and t consist only of lowercase English letters.

Follow up: Suppose there are lots of incoming s, say s1, s2, …, sk where k >= 109, and you want to check one by one to see if t has its subsequence. In this scenario, how would you change your code?

## Solution

```
class Solution {
public boolean isSubsequence(String s, String t) {
var t_i = 0;
for (var s_c : s.toCharArray()) {
var found = false;
while (t_i < t.length()) {
if (s_c == t.charAt(t_i)) {
found = true;
}
t_i += 1;
if (found) {
break;
}
}
if (!found) {
return false;
}
}
return true;
}
}
```