EasyNo. 2255
Count Prefixes of a Given String — LeetCode 2255 Python Solution
- Pattern
- Hash Map
- Topics
- Array, String
- Reading time
- 2 min
- Source
- leetcode.com
The problem
You are given a string array words and a string s, where words[i] and s comprise only of lowercase English letters. Return the number of strings in words that are a prefix of s.
Example
- Input
- words = ["a","b","c","ab","bc","abc"], s = "abc"
- Output
- 3
- Explanation
- The strings in words which are a prefix of s = "abc" are:
Python solution
class Solution:
def countPrefixes(self, words: List[str], s: str) -> int:
return sum(s.startswith(w) for w in words)Complexity
- Time
- O(m × n)where m and n are the lengths of the array words and the string s, respectively
- Space · auxiliary
- O(1)
Pattern: Hash Map
Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 2255. Count Prefixes of a Given String is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.
The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.
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| 0068 | Text Justification | Hard |
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Frequently asked questions
- How hard is LeetCode 2255. Count Prefixes of a Given String?
LeetCode 2255. Count Prefixes of a Given String is rated Easy on LeetCode.
- What is the time complexity of LeetCode 2255. Count Prefixes of a Given String?
The Python solution on this page runs in O(m × n), where m and n are the lengths of the array words and the string s, respectively.
- What is the space complexity of LeetCode 2255. Count Prefixes of a Given String?
The Python solution on this page uses O(1) auxiliary space.
- What topics does LeetCode 2255. Count Prefixes of a Given String cover?
LeetCode 2255. Count Prefixes of a Given String is tagged Array and String on LeetCode.