Solution: Number of Ways to Form Target String Given a Dictionary
Statement▼
You are given a list of words, where each string has the same length target, of length target can be formed using the given words under the following rules:
You must build the
targetfrom left to right.To form the
ithcharacter (0-indexed) oftarget, you can choose anykthcharacter of anyjthstring inwords, i.e.,target[i] = words[j][k].Once you use the
kthcharacter of thejthstring inwords, your next letter can't be a character from index0 throughkof any string inwords. In simple words, all characters to the left of or at indexkbecome unusable for every string, and the next letter must come from positions strictly to the right ofk.Repeat the process until you’ve formed the complete
target.
Note: You can use multiple characters from the same string in
words, as long as the rules above are followed.
Your task is to find and return the number of ways to form the string target from words. As the answer might be too large, return it modulo
Constraints:
1≤ words.length≤1000 1≤ words[i].length≤1000 All strings in
wordshave the same length.1≤ target.length≤1000 words[i]andtargetcontain only lowercase English letters.
Solution
As all words have the same length, placing them one under another creates a word grid where each column contains characters from the same position in each word. This helps to quickly find how many times a certain character appears at a specific position across all words.
In this solution, the first step is to go through the character grid and count how many times each character appears in every column. We store these counts in a frequency table, a 2D list where each row represents a column in the words, and each entry keeps track of how many times a character shows up there. This saves us time later because we don’t have to scan all the words repeatedly.
The next step is to calculate how many ways we can form the target string by gradually building it, using ...
Solution: Number of Ways to Form Target String Given a Dictionary
Statement▼
You are given a list of words, where each string has the same length target, of length target can be formed using the given words under the following rules:
You must build the
targetfrom left to right.To form the
ithcharacter (0-indexed) oftarget, you can choose anykthcharacter of anyjthstring inwords, i.e.,target[i] = words[j][k].Once you use the
kthcharacter of thejthstring inwords, your next letter can't be a character from index0 throughkof any string inwords. In simple words, all characters to the left of or at indexkbecome unusable for every string, and the next letter must come from positions strictly to the right ofk.Repeat the process until you’ve formed the complete
target.
Note: You can use multiple characters from the same string in
words, as long as the rules above are followed.
Your task is to find and return the number of ways to form the string target from words. As the answer might be too large, return it modulo
Constraints:
1≤ words.length≤1000 1≤ words[i].length≤1000 All strings in
wordshave the same length.1≤ target.length≤1000 words[i]andtargetcontain only lowercase English letters.
Solution
As all words have the same length, placing them one under another creates a word grid where each column contains characters from the same position in each word. This helps to quickly find how many times a certain character appears at a specific position across all words.
In this solution, the first step is to go through the character grid and count how many times each character appears in every column. We store these counts in a frequency table, a 2D list where each row represents a column in the words, and each entry keeps track of how many times a character shows up there. This saves us time later because we don’t have to scan all the words repeatedly.
The next step is to calculate how many ways we can form the target string by gradually building it, using ...