Problem
Given a string s and a string t, check if s is subsequence of t.
You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).
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).
Example 1:
s = "abc", t = "ahbgdc"Return true.
Example 2:
s = "axc", t = "ahbgdc"Return false.
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?Solution
Basic greedy
class Solution { public boolean isSubsequence(String s, String t) { if (s == null) return true; else if (t == null || t.length() < s.length()) return false; int i = 0, j = 0; while (i < s.length() && j < t.length()) { if (s.charAt(i) == t.charAt(j)) { i++; j++; } else { j++; } } return i == s.length(); }}