2565. Subsequence With the Minimum Score
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You are given two strings s and t.
You are allowed to remove any number of characters from the string t.
The score of the string is 0 if no characters are removed from the string t, otherwise:
- Let
leftbe the minimum index among all removed characters. - Let
rightbe the maximum index among all removed characters.
Then the score of the string is right - left + 1.
Return the minimum possible score to make t a subsequence of s.
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 = "abacaba", t = "bzaa" Output: 1 Explanation: In this example, we remove the character "z" at index 1 (0-indexed). The string t becomes "baa" which is a subsequence of the string "abacaba" and the score is 1 - 1 + 1 = 1. It can be proven that 1 is the minimum score that we can achieve.
Example 2:
Input: s = "cde", t = "xyz" Output: 3 Explanation: In this example, we remove characters "x", "y" and "z" at indices 0, 1, and 2 (0-indexed). The string t becomes "" which is a subsequence of the string "cde" and the score is 2 - 0 + 1 = 3. It can be proven that 3 is the minimum score that we can achieve.
Constraints:
1 <= s.length, t.length <= 105sandtconsist of only lowercase English letters.
Hints
Hint 1
Maintain two pointers: i and j. We need to perform a similar operation: while t[0:i] + t[j:n] is not a subsequence of the string s, increase j.
Hint 2
We can check the condition greedily. Create the array leftmost[i] which denotes minimum index k, such that in prefix s[0:k] exists subsequence t[0:i]. Similarly, we define rightmost[i].
Hint 3
If leftmost[i] < rightmost[j] then t[0:i] + t[j:n] is the subsequence of s.