LeetCode: isSubsequence, given with two strings return true if `s` is subsequence of `t` .

isSubsequence.java

class Solution {
    public boolean isSubsequence(String s, String t) {
        var slen = s.length();
        var tlen = t.length();
        if (slen == 0){
            return true;
        }
        if (tlen < slen){
            return false;
        }
        var sc = 0;
        for (int i = 0; i < tlen; i++){
            if (sc < slen && s.charAt(sc) == t.charAt(i)){
                sc++;
            }
        }
        
        return (sc == slen);
    }
}

Example

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).

Observation

The above problem has been solved using an algorithm with two different implementations.

Algorithm

• if the s length is equal to zero then return true.
• if the t length is less than the s length then return false.
• A marker that iterates through the s character after it's seen in 't'
• if the marker is equal to s length then return true else false.

Implementation 1

Using the s.toCharArray(). This implementation beats 54% of the total solutions submitted with a runtime of 2 ms.

Implementation 2

Using s.charAt(i) to iterate through the strings given instead of the array index. This implementation beats 89% of total solutions submitted with a runtime of 1 ms.

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