main.py

# Source: https://leetcode.com/problems/is-subsequence
# Title: Is Subsequence
# Difficulty: Easy
# Author: Mu Yang <http://muyang.pro>

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# Given two strings `s` and `t`, return `true` if `s` is a **subsequence** of `t`, or `false` otherwise.
#
# A **subsequence** of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., `"ace"` is a subsequence of `"abcde"` while `"aec"` is not).
#
# **Example 1:**
#
# ```
# Input: s = "abc", t = "ahbgdc"
# Output: true
# ```
#
# **Example 2:**
#
# ```
# Input: s = "axc", t = "ahbgdc"
# Output: false
# ```
#
# **Constraints:**
#
# - `0 <= s.length <= 100`
# - `0 <= t.length <= 10^4`
# - `s` and `t` consist only of lowercase English letters.
#
# **Follow up:** Suppose there are lots of incoming `s`, say `s_1, s_2, ..., s_k` where `k >= 10^9`, and you want to check one by one to see if `t` has its subsequence. In this scenario, how would you change your code?
#
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class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        m, n = len(s), len(t)

        i, j = 0, 0

        while i < m and j < n:
            if s[i] == t[j]:
                i += 1
            j += 1

        return i == m