How do you solve Can Convert String in K Moves on LeetCode?

Can Convert String in K Moves (LeetCode #1540) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Shifting characters wraps around after 26 shifts, so we can use modulo 26 to simplify calculations.

What is the brute force solution for Can Convert String in K Moves?

The brute force approach for Can Convert String in K Moves is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach involves trying every possible combination of shifts for each character in the string. This means we would check if we can convert each character in 's' to 't' within the given number of moves, k. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Can Convert String in K Moves?

Can Convert String in K Moves uses the following concepts: Hash Table, String. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Can Convert String in K Moves?

Always clarify the problem constraints and edge cases before diving into coding. Think about how to optimize your solution after implementing the brute force version. Practice explaining your thought process clearly, as communication is key in interviews.

What are common mistakes when solving Can Convert String in K Moves?

Not considering the wrapping nature of the alphabet when calculating shifts. Failing to account for the maximum number of shifts allowed for each character.

#1540

Can Convert String in K Moves

Medium

Hash TableStringHash 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 solution leverages the fact that shifting a character by x times is equivalent to shifting it by x % 26 times. We can group characters by their required shifts and ensure that we can perform the shifts within the allowed moves.

⚙️

Algorithm

3 steps

1Step 1: Create an array to count the number of shifts needed for each character (0-25).
2Step 2: For each character in 's', calculate the required shift to match 't' and update the count array.
3Step 3: For each unique shift value, calculate how many moves are needed and check if they fit within k.

solution.py11 lines

1def canConvertString(s, t, k):
2    count = [0] * 26
3    for i in range(len(s)):
4        shift = (ord(t[i]) - ord(s[i]) + 26) % 26
5        if shift > 0:
6            count[shift] += 1
7    for i in range(1, 26):
8        if count[i] > 0:
9            if i * (count[i]) + (count[i] - 1) * 26 > k:
10                return False
11    return True

ℹ

Complexity note: The time complexity is O(n) because we only iterate through the strings a couple of times. The space complexity is O(1) since we are using a fixed-size array to count shifts.

1Shifting characters wraps around after 26 shifts, so we can use modulo 26 to simplify calculations.
2The number of moves required for each unique shift can be calculated and compared against k.

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