What is the brute force solution for Find the Sequence of Strings Appeared on the Screen?

The brute force approach for Find the Sequence of Strings Appeared on the Screen is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach involves simulating every possible string that can be formed by pressing the keys until we reach the target. We start from an empty string and explore all combinations of appending 'a' and changing the last character. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Find the Sequence of Strings Appeared on the Screen?

Find the Sequence of Strings Appeared on the Screen uses the following concepts: String, Simulation. The recommended patterns to study are: Simulation, String Manipulation.

What are the interview tips for Find the Sequence of Strings Appeared on the Screen?

Always clarify the problem statement and constraints before jumping into coding. Think about edge cases, such as an empty target string or a target string with repeated characters. Explain your thought process as you code; it shows your understanding and can help you catch mistakes.

What are common mistakes when solving Find the Sequence of Strings Appeared on the Screen?

Failing to account for the wrap-around from 'z' to 'a' when changing characters. Not realizing that appending 'a' is necessary to build the string before changing characters.

#3324

Find the Sequence of Strings Appeared on the Screen

Medium

StringSimulationSimulationString 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)

The optimal approach leverages the fact that we can directly generate the required strings in a systematic way without exploring all combinations. We focus on appending 'a' and then changing the last character as needed, which allows us to build the target string efficiently.

⚙️

Algorithm

3 steps

1Step 1: Initialize an empty list to store the results.
2Step 2: Start with an empty string and append 'a' until the length of the string equals the length of the target.
3Step 3: For each character in the target, change the last character of the string to match the target's character.

solution.py11 lines

1def find_sequence(target):
2    result = []
3    current = ''
4    for _ in range(len(target)):
5        current += 'a'
6        result.append(current)
7    for i in range(len(target)):
8        while current[i] != target[i]:
9            current = current[:-1] + chr((ord(current[-1]) - 96) % 26 + 97)
10            result.append(current)
11    return result

ℹ

Complexity note: The time complexity is O(n) because we only go through the target string a limited number of times, directly generating the necessary strings without exploring all combinations.

1The sequence of strings is built incrementally, allowing us to visualize the process of typing.
2Understanding the character manipulation is key to optimizing the solution.

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