What is the brute force solution for Change Minimum Characters to Satisfy One of Three Conditions?

The brute force approach for Change Minimum Characters to Satisfy One of Three Conditions is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach checks every possible character change for both strings to see how many operations are needed to satisfy one of the three conditions. It's straightforward but inefficient, as it evaluates all characters in the alphabet for each character in the strings. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Change Minimum Characters to Satisfy One of Three Conditions?

Change Minimum Characters to Satisfy One of Three Conditions uses the following concepts: Hash Table, String, Counting, Prefix Sum. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Change Minimum Characters to Satisfy One of Three Conditions?

Clarify the problem requirements and constraints before diving into coding. Think about edge cases, such as when both strings are already satisfying one condition. Explain your thought process clearly while coding, as it helps the interviewer understand your approach.

What are common mistakes when solving Change Minimum Characters to Satisfy One of Three Conditions?

Failing to consider all three conditions when calculating operations. Not accounting for the distinct character condition properly.

#1737

Change Minimum Characters to Satisfy One of Three Conditions

Medium

Hash TableStringCountingPrefix SumHash MapArray

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

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

💡

Intuition

Time O(n)Space O(1)

The optimal approach leverages the properties of characters in the strings to minimize operations by calculating the necessary changes based on the smallest and largest characters in both strings. This avoids redundant checks and significantly reduces the number of operations needed.

⚙️

Algorithm

5 steps

1Step 1: Find the minimum and maximum characters in both strings 'a' and 'b'.
2Step 2: Calculate the number of changes needed to make all characters in 'a' less than the minimum character of 'b'.
3Step 3: Calculate the number of changes needed to make all characters in 'b' less than the minimum character of 'a'.
4Step 4: Calculate the number of changes needed to make both strings consist of the same character, which is the minimum character of either string.
5Step 5: Return the minimum of the three calculated operations.

solution.py7 lines

1def min_operations(a, b):
2    min_a, max_a = min(a), max(a)
3    min_b, max_b = min(b), max(b)
4    ops1 = sum(1 for x in a if x >= min_b) + len(b)
5    ops2 = sum(1 for y in b if y >= min_a) + len(a)
6    ops3 = len(a) + len(b) - (a.count(min_a) + b.count(min_a))
7    return min(ops1, ops2, ops3)

ℹ

Complexity note: The time complexity is O(n) because we only need to traverse each string a constant number of times (to find min/max and calculate operations). The space complexity is O(1) since we are using a constant amount of extra space.

1Understanding character relationships is crucial for minimizing operations.
2Iterating through the alphabet can help identify optimal character changes.

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