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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"

Constraints:

  • 1 <= str.length <= 12
  • str consists of lowercase English letters, uppercase English letters, and digits.

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A

Athanasios Petsas

· 4 years ago

In C++ sollution, we don't need to transform the string to an array of chars for doing the upper/lower case change and then transform it back to add it to the result vector; we can just do it in place. Here's the code having this change:

{code} static vector findLetterCaseStringPermutations(const string& str) { vector permutations; if (str == "") { return permutations; }

permutations.push_back(str); // process every character of the string one by one for (int i = 0; i < str.length(); i++) { if (!isalpha(str[i])) // only process characters, skip digits continue; // we'll take all existing permutations and change the letter case appropriately int n = permutations.size(); for (int j = 0; j < n; j++) { string newPerm = permutations[j]; // if the current char is in upper case change it to lo