Number of Ways to Form a Target String Given a Dictionary

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 i ^th character ( 0-indexed ) of target , you can choose the k ^th character of the j ^th string in words if target[i] = words[j][k] .

Once you use the k ^th character of the j ^th string of words , you can no longer use the x ^th 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 10 ^9 + 7 .