Leetcode Problem 1415. The k-th Lexicographical String of All Happy Strings of Length n

1415. The k-th Lexicographical String of All Happy Strings of Length n

Leetcode Solutions

Backtracking Approach

  1. Define a helper function backtrack that takes the current path (string being built) and the position to insert the next character.
  2. If the length of the path is equal to n, decrement k and check if k is zero. If so, store the current path as the answer.
  3. If k is not zero, iterate over the characters 'a', 'b', and 'c'.
  4. For each character, check if it can be added to the path (i.e., it is not the same as the last character in the path).
  5. If the character can be added, append it to the path and recursively call backtrack with the updated path and position.
  6. If the character cannot be added or if k reaches zero, backtrack by removing the last character from the path.
  7. After exploring all possibilities, return the answer if k is zero; otherwise, return an empty string.
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Iterative BFS Approach

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