Leetcode Problem 1639. Number of Ways to Form a Target String Given a Dictionary

Algorithm

1. Initialize a matrix charOccurrences with zeros.
2. Iterate over each column col and each word in words to fill charOccurrences with the count of each character.
3. Initialize a DP matrix dp with zeros.
4. Set dp[0][0] = 1 as the base case.
5. For each length from 0 to targetLength, and for each col from 0 to wordLength - 1, do the following:
   • If length < targetLength, update dp[length + 1][col + 1] by adding charOccurrences[target[length] - 'a'][col] * dp[length][col].
   • Update dp[length][col + 1] by adding dp[length][col].
6. Return dp[targetLength][wordLength] as the result.