Wildcard Queries

Posted: 31 Jul, 2021
Difficulty: Hard

PROBLEM STATEMENT

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You are given a dictionary ‘D’ consisting of ‘N’ words. Each word of the dictionary is of fixed size ‘L’ and contains only lowercase English alphabets.

Now you have to answer ‘Q’ queries, in each query you are given a word ‘W’ of fixed size ‘L’ but this word can consist of either lowercase English alphabets or ‘?’ (wildcard characters). Where ‘?’ can be matched by any lowercase English alphabet.

For each query find how many words in the dictionary can be matched by the query word ‘W’ by replacing ‘?’(if present) with some lowercase English alphabet.

 

Example :
If the dictionary is: {"cat", "rat", "bat", "hat"}

And query words are "?at" and "b?t", then:

"?at" => can be matched by all the 4 dictionary words by replacing '?' with 'c', 'r', 'b' or 'h'.

"b?t" => can only be matched by the dictionary word "bat" by replacing '?' with 'a'.  
Input Format :
The first line contains a single integer ‘T’ denoting the number of test cases. Then each test case follows.

The first line of each test case contains two integers ‘N’ and ‘L’, where N denotes the number of words in the dictionary and L denotes the length of words in the dictionary and queries.

The next line contains N words each of size L, denoting the words in the dictionary.

The next line contains a single integer ‘Q’ denoting the number of queries.

The following Q lines, each contains a word ‘W’ of size L, denoting the query word.
Output Format :
For each test case print Q integers in a separate line, each denoting the number of dictionary words that can be matched by the query word.

Output for each test case will be printed in a separate line.
Note :
You are not required to print anything; it has already been taken care of. Just implement the function.
Constraints :
1 <= T <= 10      
1 <= N <= 100
1 <= L <= 7
1 <= Q <= 100
1 <= word.size <= L

Time limit: 1 sec
Approach 1

Store the dictionary words in a hash-map for a constant lookup time, now for each query word, try replacing each ‘?’ with every possible lowercase alphabet and generating all possible words that can be formed by the query word, for each of them: search whether it exists in the dictionary or not.

The steps are as follows:

  1. Initialize finalAnswer array to store the answer to each query.
  2. Initialize a hash-map mp. And store all the dictionary words in it.
  3. For each query initialize count = 0 and generate all possible words that can be formed by replacing ‘?’ using backtracking.
  4. For each generated word, increment count if it exists in hash-map mp.
  5. Print the insert the value of count after generating all the words in the finalAnswer array.
  6. Move to the next query and repeat the same thing from 2nd Step.
  7. When all the queries have been processed return the finalAnswer array
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