3291. Minimum Number of Valid Strings to Form Target I
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You are given an array of strings words and a string target.
A string x is called valid if x is a prefix of any string in words.
Return the minimum number of valid strings that can be concatenated to form target. If it is not possible to form target, return -1.
Example 1:
Input: words = ["abc","aaaaa","bcdef"], target = "aabcdabc"
Output: 3
Explanation:
The target string can be formed by concatenating:
- Prefix of length 2 of
words[1], i.e."aa". - Prefix of length 3 of
words[2], i.e."bcd". - Prefix of length 3 of
words[0], i.e."abc".
Example 2:
Input: words = ["abababab","ab"], target = "ababaababa"
Output: 2
Explanation:
The target string can be formed by concatenating:
- Prefix of length 5 of
words[0], i.e."ababa". - Prefix of length 5 of
words[0], i.e."ababa".
Example 3:
Input: words = ["abcdef"], target = "xyz"
Output: -1
Constraints:
1 <= words.length <= 1001 <= words[i].length <= 5 * 103- The input is generated such that
sum(words[i].length) <= 105. words[i]consists only of lowercase English letters.1 <= target.length <= 5 * 103targetconsists only of lowercase English letters.
Hints
Hint 1
Let
dp[i] be the minimum cost to form the prefix of length i of target.Hint 2
If
target[(i + 1)..j] matches any prefix, update the range dp[(i + 1)..j] to minimum between original value and dp[i] + 1.Hint 3
Use a Trie to check prefix matching.