Is Subsequence

Given a stringsand a stringt, check ifsis subsequence oft.

You may assume that there is only lower case English letters in bothsandt.tis 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"

Returntrue.

Example 2: s="axc", t="ahbgdc"

Returnfalse.

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?

Note

同向双指针分别指向两个字符串

Code

class Solution {
    public boolean isSubsequence(String s, String t) {
        int i = 0, j = 0;
        if (s.length() > t.length()) {
            return false;
        }

        while (i < s.length() && j < t.length()) {
            if (s.charAt(i) == t.charAt(j)) {
                i++;
            }
            j++;
        }

        return i == s.length();
    }
}