How do you solve Hash Divided String on LeetCode?

Hash Divided String (LeetCode #3271) 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 to break down the string into substrings is crucial.

What is the brute force solution for Hash Divided String?

The brute force approach for Hash Divided String is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach involves iterating through each substring of length k, calculating the hash value for each character, and summing them up. This method is straightforward but inefficient due to repeated calculations. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Hash Divided String?

Hash Divided String uses the following concepts: String, Simulation. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Hash Divided String?

Clarify the input constraints and assumptions before diving into coding. Explain your thought process while coding to show your understanding. Test your code with edge cases to ensure robustness.

What are common mistakes when solving Hash Divided String?

Not correctly handling the substring extraction. Forgetting to apply the modulo operation correctly.

#3271

Hash Divided String

Medium

StringSimulationHash MapArray

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

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

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Intuition

Time O(n)Space O(n)

The optimal solution improves efficiency by directly calculating the hash values without unnecessary iterations. By using a single loop to process the string, we reduce the time complexity significantly.

⚙️

Algorithm

6 steps

1Step 1: Initialize an empty string result to store the final hashed characters.
2Step 2: Loop through the string s in increments of k to extract each substring.
3Step 3: For each substring, calculate the sum of the hash values of its characters in a single pass.
4Step 4: Compute the remainder of the sum when divided by 26 to get hashedChar.
5Step 5: Convert hashedChar back to a character and append it to result.
6Step 6: Return the result string.

solution.py9 lines

1# Full working Python code
2
3def hash_divided_string(s, k):
4    result = ''
5    for i in range(0, len(s), k):
6        hash_sum = sum(ord(s[j]) - ord('a') for j in range(i, i + k))
7        hashedChar = hash_sum % 26
8        result += chr(hashedChar + ord('a'))
9    return result

ℹ

Complexity note: The time complexity is O(n) because we are processing each character exactly once. The space complexity is O(n) due to the storage of the result string.

1Understanding how to break down the string into substrings is crucial.
2Hashing characters based on their position in the alphabet is a common technique.

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