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Tested Python solution for LeetCode 2486 with 22 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 2486 # by problem number
lcpy gen -s append_characters_to_string_to_make_subsequence # by problem name
s and t consisting of only lowercase English letters.
Return the minimum number of characters that need to be appended to the end of s so that t becomes a subsequence of s.
A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.
Input: s = "coaching", t = "coding"
Output: 4
Explanation: Append the characters "ding" to the end of s so that s = "coachingding".
Now, t is a subsequence of s ("coachingding").
It can be shown that appending any 3 characters to the end of s will never make t a subsequence.
Input: s = "abcde", t = "a"
Output: 0
Explanation: t is already a subsequence of s ("abcde").
Input: s = "z", t = "abcde"
Output: 5
Explanation: Append the characters "abcde" to the end of s so that s = "zabcde".
Now, t is a subsequence of s ("zabcde").
It can be shown that appending any 4 characters to the end of s will never make t a subsequence.
class Solution:
# Time: O(len(s) + len(t))
# Space: O(1)
def append_characters(self, s: str, t: str) -> int:
i = 0
for ch in s:
if i == len(t):
break
if ch == t[i]:
i += 1
return len(t) - i
| Time | Space |
|---|---|
| O(len(s) + len(t)) | O(1) |