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Wildcard Matching

Certification: Advanced Level Accuracy: 100% Submissions: 1 Points: 15

Write a Java program to implement wildcard pattern matching with support for '?' and '*' characters.

  • '?' Matches any single character.
  • '*' Matches any sequence of characters (including an empty sequence).

The matching should cover the entire input string (not partial).

Example 1
    
  
  • Input: pattern = "a*c", text = "abc"
    • 
  
  • Output: true
    • 
  
  • Explanation: 
    
    Step 1: The pattern "a*c" needs to match with text "abc".
    
    Step 2: 'a' matches the first character 'a' in the text.
    
    Step 3: '*' can match any sequence - in this case it matches 'b'.
    
    Step 4: 'c' matches the last character 'c' in the text.
    
    Step 5: The entire text is matched, so return true.
  
    •
Example 2
    
  
  • Input: pattern = "a?c", text = "abcd"
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  • Output: false
    • 
  
  • Explanation: 
    
    Step 1: The pattern "a?c" needs to match with text "abcd".
    
    Step 2: 'a' matches the first character 'a' in the text.
    
    Step 3: '?' matches any single character - in this case it matches 'b'.
    
    Step 4: 'c' matches the third character 'c' in the text.
    
    Step 5: The pattern is completely matched, but there's still 'd' left in the text.
    
    Step 6: Since the entire text is not matched by the pattern, return false.
  
    •
Constraints
    
  
  • 0 <= pattern.length, text.length <= 1000
    • 
  
  • Pattern and text consist only of lowercase English letters and the wildcard characters '?' and '*'
    • 
  
  • Time Complexity: O(m*n) where m and n are the lengths of the pattern and text respectively
    • 
  
  • Space Complexity: O(m*n)
    •
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Hint
Solution

Solution Hints

    
  
  • Use dynamic programming to solve this problem.
    • 
  
  • Create a 2D boolean array dp[i][j] which represents if the first i characters of text match the first j characters of pattern.
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  • Initialize base cases: empty pattern matches empty string, and handle asterisks in the pattern.
    • 
  
  • For each character pair, update dp[i][j] based on current characters and previous matching states.
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  • Handle '?' by checking if the previous characters match.
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  • Handle '*' by considering both zero and multiple character matches.
    •

Steps to solve by this approach:

 Step 1: Create a 2D boolean array dp[m+1][n+1] where m is the length of text and n is the length of pattern.

 Step 2: Initialize dp[0][0] as true since empty pattern matches empty text.

 Step 3: Handle the case where pattern starts with "*" characters.

 Step 4: Iterate through each character of text and pattern to fill the dp table.

 Step 5: For each cell, determine match status based on current characters and previous states.

 Step 6: If the current pattern character is "*", it can match zero characters (dp[i][j-1]) or one or more characters (dp[i-1][j]).

 Step 7: If the current pattern character is "?" or matches the text character, the result depends on whether previous substrings match (dp[i-1][j-1]).

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