Add is subsequence

Author: onixlas

two-pointers/392_is_subsequence/README.md

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+# Is Subsequence
+
+## Problem Description
+
+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.
+
+## Solution
+
+```python
+def is_subsequence(self, s: str, t: str) -> bool:
+    """
+    Check if string `s` is a subsequence of string `t`.
+
+    A subsequence is a sequence that can be derived from another sequence by deleting zero or more elements
+    without changing the order of the remaining elements.
+
+    :param self: The instance reference (for method implementation)
+    :param s: The potential subsequence string to check
+    :param t: The string in which to search for the subsequence
+    :return: True if `s` is a subsequence of `t`, False otherwise
+    """
+    s_pointer = 0
+    s_length = len(s)
+
+    if not s_length:
+        return True
+
+    for t_pointer in range(len(t)):
+        if s[s_pointer] == t[t_pointer]:
+            s_pointer += 1
+        if s_pointer == s_length:
+            return True
+
+    return False
+```
+
+* **Time Complexity:** $O(n)$
+* **Space Complexity:** $O(1)$

two-pointers/392_is_subsequence/solution.py

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+def is_subsequence(self, s: str, t: str) -> bool:
+    """
+    Check if string `s` is a subsequence of string `t`.
+
+    A subsequence is a sequence that can be derived from another sequence by deleting zero or more elements
+    without changing the order of the remaining elements.
+
+    :param self: The instance reference (for method implementation)
+    :param s: The potential subsequence string to check
+    :param t: The string in which to search for the subsequence
+    :return: True if `s` is a subsequence of `t`, False otherwise
+    """
+    s_pointer = 0
+    s_length = len(s)
+
+    if not s_length:
+        return True
+
+    for t_pointer in range(len(t)):
+        if s[s_pointer] == t[t_pointer]:
+            s_pointer += 1
+        if s_pointer == s_length:
+            return True
+
+    return False
+
+
+assert is_subsequence(s='abc', t='ahbgdc') == True, 'Test 1 Failed'
+assert is_subsequence(s='axc', t='ahbgdc') == False, 'Test 2 Failed'
+assert is_subsequence(s='', t='ahbgdc') == True, 'Test 3 Failed'