【LeetCode】 392. Is Subsequence

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?

public class Solution {
public boolean isSubsequence(String s, String t) {
if (s.isEmpty()) {
return true;
}
int p1 = 0, flag = 0;
char[] c1 = s.toCharArray(), c2 = t.toCharArray();
for (int p2 = 0; p2 < c2.length; p2++) {
if (c1[p1] == c2[p2]) {
p1++;
}
if (p1 == c1.length) {
flag = 1;
break;
}
}
return flag == 1;
}
}