2486 - Append Characters to String to Make Subsequence\.

Medium

You are given two strings s and t consisting of only lowercase English letters.

Return the minimum number of characters that need to be appended to the end of s so that t becomes a subsequence of s.

A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.

Example 1:

Input: s = "coaching", t = "coding"

Output: 4

Explanation: Append the characters "ding" to the end of s so that s = "coachingding". Now, t is a subsequence of s ("<ins> co </ins>aching<ins> ding </ins>"). It can be shown that appending any 3 characters to the end of s will never make t a subsequence.

Example 2:

Input: s = "abcde", t = "a"

Output: 0

Explanation: t is already a subsequence of s ("<ins> a </ins>bcde").

Example 3:

Input: s = "z", t = "abcde"

Output: 5

Explanation: Append the characters "abcde" to the end of s so that s = "zabcde". Now, t is a subsequence of s ("z<ins> abcde </ins>"). It can be shown that appending any 4 characters to the end of s will never make t a subsequence.

Constraints:

• <code>1 <= s.length, t.length <= 10⁵</code>

• s and t consist only of lowercase English letters.