2490. Circular Sentence - Explanation

1. Splitting the String

class Solution:
    def isCircularSentence(self, sentence: str) -> bool:
        w = sentence.split(" ")

        for i in range(len(w)):
            if w[i][0] != w[i - 1][-1]:
                return False

        return True

Time & Space Complexity

Time complexity: $O(n)$
Space complexity: $O(n)$

2. Iteration (Space Optimized)

class Solution:
    def isCircularSentence(self, sentence: str) -> bool:
        for i in range(len(sentence)):
            if sentence[i] == " " and sentence[i - 1] != sentence[i + 1]:
                return False
        return sentence[0] == sentence[-1]

Time & Space Complexity

Time complexity: $O(n)$
Space complexity: $O(1)$