2255. Count Prefixes of a Given String
Description
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
.
A prefix of a string is a substring that occurs at the beginning of the string. A substring is a contiguous sequence of characters within a string.
Example 1:
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: "a", "ab", and "abc". Thus the number of strings in words which are a prefix of s is 3.
Example 2:
Input: words = ["a","a"], s = "aa" Output: 2 Explanation: Both of the strings are a prefix of s. Note that the same string can occur multiple times in words, and it should be counted each time.
Constraints:
1 <= words.length <= 1000
1 <= words[i].length, s.length <= 10
words[i]
ands
consist of lowercase English letters only.
Solutions
Solution 1: Traversal Counting
We directly traverse the array words, and for each string w, we check if s starts with w as a prefix. If it does, we increment the answer by one.
After the traversal, we return the answer.
The time complexity is $O(m \times n)$, where $m$ and $n$ are the lengths of the array words and the string s, respectively. The space complexity is $O(1)$.
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