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3474. Lexicographically Smallest Generated String

Description

You are given two strings, str1 and str2, of lengths n and m, respectively.

A string word of length n + m - 1 is defined to be generated by str1 and str2 if it satisfies the following conditions for each index 0 <= i <= n - 1:

  • If str1[i] == 'T', the substring of word with size m starting at index i is equal to str2, i.e., word[i..(i + m - 1)] == str2.
  • If str1[i] == 'F', the substring of word with size m starting at index i is not equal to str2, i.e., word[i..(i + m - 1)] != str2.

Return the lexicographically smallest possible string that can be generated by str1 and str2. If no string can be generated, return an empty string "".

 

Example 1:

Input: str1 = "TFTF", str2 = "ab"

Output: "ababa"

Explanation:

The table below represents the string "ababa"

Index T/F Substring of length m
0 'T' "ab"
1 'F' "ba"
2 'T' "ab"
3 'F' "ba"

The strings "ababa" and "ababb" can be generated by str1 and str2.

Return "ababa" since it is the lexicographically smaller string.

Example 2:

Input: str1 = "TFTF", str2 = "abc"

Output: ""

Explanation:

No string that satisfies the conditions can be generated.

Example 3:

Input: str1 = "F", str2 = "d"

Output: "a"

 

Constraints:

  • 1 <= n == str1.length <= 104
  • 1 <= m == str2.length <= 500
  • str1 consists only of 'T' or 'F'.
  • str2 consists only of lowercase English characters.

Solutions

Solution 1

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