(Leetcode Challenge) Is Subsequence

2020-06-09 Jun Young ChoiAlgorithm

Description:

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.

Code:

class Solution {
    public boolean isSubsequence(String pattern, String original) {
        
        boolean result = false;
        int hitIdx = 0;
        
        // pattern str == ""
        if("".equals(pattern)) {
            result = true;
            return result;
        }
        
        char[] patternAry = pattern.toCharArray();
        char[] originalAry = original.toCharArray();
        
        for(int idx=0; idx<original.length(); idx+=1) {
            if(patternAry[hitIdx] == originalAry[idx]) {
                hitIdx += 1;
                if(hitIdx == patternAry.length) {
                    result = true;
                    break;
                }
            }
        }
        return result;
    }
}