How do you solve Rearrange K Substrings to Form Target String on LeetCode?

Rearrange K Substrings to Form Target String (LeetCode #3365) 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: Both strings must be anagrams, ensuring they contain the same characters.

What is the brute force solution for Rearrange K Substrings to Form Target String?

The brute force approach for Rearrange K Substrings to Form Target String is Brute Force, with O(n²) time complexity and O(1) space complexity. We can generate all possible ways to split the string `s` into `k` substrings and check if any rearrangement of these substrings can form the string `t`. This is straightforward but inefficient. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Rearrange K Substrings to Form Target String?

Rearrange K Substrings to Form Target String uses the following concepts: Hash Table, String, Sorting. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Rearrange K Substrings to Form Target String?

Always start with edge cases, like checking lengths before diving into logic. Think about character frequency as a way to simplify the problem. Explain your thought process clearly; it helps interviewers understand your approach.

What are common mistakes when solving Rearrange K Substrings to Form Target String?

Not checking if the length of `s` is divisible by `k` before proceeding. Assuming that generating permutations is the only way to check for rearrangement.

#3365

Rearrange K Substrings to Form Target String

Medium

Hash TableStringSortingHash MapArray

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)

Instead of generating permutations, we can directly check if the frequency of characters in `s` can be rearranged into `t` by counting the characters in each substring and ensuring they can be grouped correctly.

⚙️

Algorithm

3 steps

1Step 1: Check if the length of `s` is divisible by `k`. If not, return false.
2Step 2: Count the frequency of characters in `s` and `t`.
3Step 3: For each character, check if its frequency in `s` can be evenly distributed into `k` substrings.

solution.py13 lines

1# Full working Python code
2from collections import Counter
3
4def can_form_target(s, t, k):
5    n = len(s)
6    if n % k != 0:
7        return False
8    count_s = Counter(s)
9    count_t = Counter(t)
10    for char in count_s:
11        if count_s[char] % k != 0 or count_s[char] != count_t[char]:
12            return False
13    return True

ℹ

Complexity note: The time complexity is O(n) because we only traverse the strings a couple of times to count character frequencies, which is efficient compared to generating permutations.

1Both strings must be anagrams, ensuring they contain the same characters.
2The length of `s` must be divisible by `k` to split into equal substrings.

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