392. Is Subsequence

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.

Rust Solution

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;
            } else {
                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);
}

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