IsSubsequence.java

/*
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?

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.
*/

class Solution {
    public boolean isSubsequence(String s, String t) {
        
        boolean[][] dp = new boolean[s.length()+1][t.length()+1];
        for(int j=0; j<=t.length(); j++){
            dp[0][j] = true;
        }
        
        for(int i=1; i<=s.length(); i++){
            dp[i][0] = false;
        }
        
        for(int i=1; i<=s.length(); i++){
            for(int j=1; j<=t.length(); j++){
                if(s.charAt(i-1) == t.charAt(j-1)){
                    dp[i][j] = dp[i-1][j-1];
                }
                else{
                    dp[i][j] = dp[i][j-1];
                }
            }
        }
        return dp[s.length()][t.length()];
    }
}