How do you solve Lexicographically Smallest Generated String on LeetCode?

Lexicographically Smallest Generated String (LeetCode #3474) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Understanding how 'T' and 'F' conditions affect string generation.

What is the time complexity of Lexicographically Smallest Generated String?

The optimal solution for Lexicographically Smallest Generated String runs in O(n) time and uses O(n) space. Linear time complexity due to a single pass through str1 and filling the result array.

What is the brute force solution for Lexicographically Smallest Generated String?

The brute force approach for Lexicographically Smallest Generated String is Brute Force, with O(n²) time complexity and O(1) space complexity. Generate all possible strings by trying every combination of substrings based on 'T' and 'F' in str1. Check each string to see if it meets the conditions. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Lexicographically Smallest Generated String?

Lexicographically Smallest Generated String uses the following concepts: String, Greedy, String Matching. The recommended patterns to study are: Greedy, String Manipulation.

What are the interview tips for Lexicographically Smallest Generated String?

Clarify the problem constraints before coding. Think about edge cases, such as empty strings. Explain your thought process while coding.

What are common mistakes when solving Lexicographically Smallest Generated String?

Not handling overlapping conditions correctly. Ignoring the need to check against str2 for 'F' conditions.

#3474

Lexicographically Smallest Generated String

Hard

StringGreedyString MatchingGreedyString Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

Use a greedy approach to build the result string by filling in the constraints from str1 while ensuring the smallest lexicographical order.

⚙️

Algorithm

3 steps

1Step 1: Initialize an empty result string.
2Step 2: Iterate through str1, appending str2 or the smallest lexicographical character as needed.
3Step 3: Ensure that 'F' conditions are satisfied by checking against str2.

solution.py9 lines

1def generate_strings(str1, str2):
2    n, m = len(str1), len(str2)
3    result = [''] * (n + m - 1)
4    for i in range(n):
5        if str1[i] == 'T':
6            result[i:i + m] = str2
7        elif result[i:i + m] == list(str2):
8            return ''
9    return ''.join(result)

ℹ

Complexity note: Linear time complexity due to a single pass through str1 and filling the result array.

1Understanding how 'T' and 'F' conditions affect string generation.
2Lexicographical order can be maintained by careful character placement.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.