How do you solve Circular Sentence on LeetCode?

Circular Sentence (LeetCode #2490) 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: The circular condition requires both the last character of each word and the last word's last character to match the first word's first character.

What is the brute force solution for Circular Sentence?

The brute force approach for Circular Sentence is Brute Force, with O(n²) time complexity and O(1) space complexity. We can check each pair of consecutive words to see if the last character of the current word matches the first character of the next word. Finally, we check if the last word's last character matches the first word's first character. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Circular Sentence?

Circular Sentence uses the following concepts: String. The recommended patterns to study are: String Manipulation, Array.

What are the interview tips for Circular Sentence?

Clarify the definition of a circular sentence before diving into the solution. Think about edge cases, such as single-word sentences. Explain your thought process clearly while coding.

What are common mistakes when solving Circular Sentence?

Not checking the circular condition between the last and first words. Overlooking case sensitivity in character comparisons.

#2490

Circular Sentence

Easy

StringString ManipulationArray

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 checking each word pair, we can directly check the first and last characters of the entire sentence after splitting it into words, which reduces unnecessary comparisons.

⚙️

Algorithm

3 steps

1Step 1: Split the sentence into words.
2Step 2: Check if the last character of the last word matches the first character of the first word.
3Step 3: Loop through the words and check if the last character of each word matches the first character of the next word.

solution.py8 lines

1def isCircularSentence(sentence):
2    words = sentence.split()
3    if words[-1][-1] != words[0][0]:
4        return False
5    for i in range(len(words) - 1):
6        if words[i][-1] != words[i + 1][0]:
7            return False
8    return True

ℹ

Complexity note: The time complexity is O(n) because we only loop through the words a couple of times, which is linear in relation to the number of characters. The space complexity is O(n) due to the storage of the words in an array.

1The circular condition requires both the last character of each word and the last word's last character to match the first word's first character.
2Efficiently checking character pairs reduces unnecessary comparisons.

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