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?

**Credits:**

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

**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 <= 10^4`

- Both strings consists only of lowercase characters.

```
struct Solution;
impl Solution {
fn is_subsequence(s: String, t: String) -> bool {
let mut i = 0;
let mut j = 0;
let n = s.len();
let m = t.len();
while i < n && j < m {
if s[i..=i] == t[j..=j] {
i += 1;
}
j += 1;
}
i == n
}
}
#[test]
fn test() {
let s = "abc".to_string();
let t = "ahbgdc".to_string();
assert_eq!(Solution::is_subsequence(s, t), true);
let s = "axc".to_string();
let t = "ahbgdc".to_string();
assert_eq!(Solution::is_subsequence(s, t), false);
}
```