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String Permutations by changing case (medium)

String Permutations by changing case (medium)

Problem Statement

Given a string, find all of its permutations preserving the character sequence but changing case.

Example 1:

Input: "ad52"
Output: "ad52", "Ad52", "aD52", "AD52"

Example 2:

Input: "ab7c"
Output: "ab7c", "Ab7c", "aB7c", "AB7c", "ab7C", "Ab7C", "aB7C", "AB7C"

Try it yourself

Try solving this question here:

import java.util.*;
class LetterCaseStringPermutation {
  public static List<String> findLetterCaseStringPermutations(String str) {
    List<String> permutations = new ArrayList<>();
    // TODO: Write your code here
    return permutations;
  }
  public static void main(String[] args) {
    List<String> result = LetterCaseStringPermutation.findLetterCaseStringPermutations("ad52");
    System.out.println(" String permutations are: " + result);
    result = LetterCaseStringPermutation.findLetterCaseStringPermutations("ab7c");
    System.out.println(" String permutations are: " + result);
  }
}

Solution

This problem follows the Subsets pattern and can be mapped to Permutations.

Let’s take Example-2 mentioned above to generate all the permutations. Following a BFS approach, we will consider one character at a time. Since we need to preserve the character sequence, we can start with the actual string and process each character (i.e., make it upper-case or lower-case) one by one:

  1. Starting with the actual string: "ab7c"
  2. Processing the first character (‘a’), we will get two permutations: "ab7c", "Ab7c"
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