Package g1601_1700.s1639_number_of_ways_to_form_a_target_string_given_a_dictionary

Class Solution

java.lang.Object
g1601_1700.s1639_number_of_ways_to_form_a_target_string_given_a_dictionary.Solution
public class Solution extends Object
1639 - Number of Ways to Form a Target String Given a Dictionary\. Hard You are given a list of strings of the **same length** `words` and a string `target`. Your task is to form `target` using the given `words` under the following rules: * `target` should be formed from left to right. * To form the ith character ( **0-indexed** ) of `target`, you can choose the kth character of the jth string in `words` if `target[i] = words[j][k]`. * Once you use the kth character of the jth string of `words`, you **can no longer** use the xth character of any string in `words` where `x <= k`. In other words, all characters to the left of or at index `k` become unusuable for every string. * Repeat the process until you form the string `target`. **Notice** that you can use **multiple characters** from the **same string** in `words` provided the conditions above are met. Return _the number of ways to form `target` from `words`_. Since the answer may be too large, return it **modulo** 109 + 7. **Example 1:** **Input:** words = ["acca","bbbb","caca"], target = "aba" **Output:** 6 **Explanation:** There are 6 ways to form target. "aba" -> index 0 ("acca"), index 1 ("bbbb"), index 3 ("caca") "aba" -> index 0 ("acca"), index 2 ("bbbb"), index 3 ("caca") "aba" -> index 0 ("acca"), index 1 ("bbbb"), index 3 ("acca") "aba" -> index 0 ("acca"), index 2 ("bbbb"), index 3 ("acca") "aba" -> index 1 ("caca"), index 2 ("bbbb"), index 3 ("acca") "aba" -> index 1 ("caca"), index 2 ("bbbb"), index 3 ("caca") **Example 2:** **Input:** words = ["abba","baab"], target = "bab" **Output:** 4 **Explanation:** There are 4 ways to form target. "bab" -> index 0 ("baab"), index 1 ("baab"), index 2 ("abba") "bab" -> index 0 ("baab"), index 1 ("baab"), index 3 ("baab") "bab" -> index 0 ("baab"), index 2 ("baab"), index 3 ("baab") "bab" -> index 1 ("abba"), index 2 ("baab"), index 3 ("baab") **Constraints:** * `1 <= words.length <= 1000` * `1 <= words[i].length <= 1000` * All strings in `words` have the same length. * `1 <= target.length <= 1000` * `words[i]` and `target` contain only lowercase English letters.

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numWays

      public int numWays(String[] words, String target)