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.
SOLUTION:
class Solution:
def countPrefixes(self, words: List[str], s: str) -> int:
n = len(s)
prefixes = set()
for i in range(1, n + 1):
prefixes.add(s[:i])
ctr = 0
for w in words:
if w in prefixes:
ctr += 1
return ctr
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