392. Is Subsequence

Posted 2020-10-11 andywu

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 sis 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?

题目含义：字符串t删减多个字母后，能否得到字符串s？

 1     public boolean isSubsequence(String s, String t) {
 2         int i=0,j=0;
 3         if (s.isEmpty()) return true;
 4         while (i<s.length() && j<t.length())
 5         {
 6             if (s.charAt(i) == t.charAt(j)){
 7                 i++;j++;
 8             }else
 9             {
10                 j++;
11             }
12         }
13         return i==s.length();        
14     }