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Scenario Preprocess String P Build Left Array Allows Us Use Bad Character Rule Efficiently Q43814495

Scenario

We have to preprocess string P to build the left array thatallows us to use the bad character rule efficiently. Recall thatleft[i][j] should return either of the following:

• The largest index k so that k <= i and P[k] == j
• -1, if j isn’t found in P

Aim

Build an array that allows us to use the bad character ruleefficiently.

Steps for Completion

1. Implement the commented part of the match() method of the classBadCharacterRule.

2. Assume that the alphabet of strings P and T consists only oflowercase letters of the English alphabet. Snippet 5.3 isshown below:

   List shifts = new ArrayList<>();int skip;for (int i = 0; i < n – m + 1; i += skip) { skip = 0; for (int j = m – 1; j >= 0; j–) { if (P.charAt(j) != T.charAt(i + j)) { skip = Math.max(1, j – left[j][T.charAt(i + j)]); break; } } if (skip == 0) { shifts.add(i); skip = 1; }}

   Snippet 5.3: Using the bad character rule to improveour skips

Code Given:

import java.util.ArrayList;
import java.util.List;

public class BadCharacterRule {
public List match(String P, String T) {
int n = T.length();
int m = P.length();

int e = 256;
int left[][] = new int[m][e];
// Populate left[][] with the correct values

// Add the code from Snippet 5.3 to search thestring using bcr
return shifts;
}

public static void main(String[] args) {
}

}

With using the “Code Given”information, add in code from the Snippet 5.3 to search the stringusing BCR (Bad Character Rule). The Snippet 5.3 is shown in the”Steps for Completion” information.  

Expert Answer

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Answer to Scenario We have to preprocess string P to build the left array that allows us to use the bad character rule efficiently…