LeetCode-in-Java

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 (“coachingding”). 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 (“abcde”).

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 (“zabcde”). It can be shown that appending any 4 characters to the end of s will never make t a subsequence.

Constraints:

Solution

public class Solution {
    public int appendCharacters(String s, String t) {
        int lengthOfT = t.length();
        int indexOfT = 0;
        int indexOfS = 0;
        int position;
        if (s.contains(t)) {
            return 0;
        }
        while (indexOfT < lengthOfT) {
            position = s.indexOf(t.charAt(indexOfT), indexOfS);
            if (position < 0) {
                return lengthOfT - indexOfT;
            }
            indexOfS = position;
            indexOfT++;
            indexOfS++;
        }
        return lengthOfT - (indexOfT);
    }
}