392. is subsequence

class Solution:
    def isSubsequence(self, s, t):
        if not s:
            return True
        index = 0
        for c in t:
            if c == s[index]:
                index += 1
                if index == len(s):
                    return True
        return False

class Solution:
    def isSubsequence(self, s, t):
        index = -1
        for c in s:
            index = t.find(c, index + 1)
            if index == -1:
                return False
        return True