Problem URL: Index pairs of a string

We will first create a set of all the words in words. Then, we will iterate through text and check if the current word is in the set. If it is, we will add the current index and the current index plus the length of the current word minus one to the result.

class Solution:
    def indexPairs(self, text: str, words: List[str]) -> List[List[int]]:
        result = []
        words = set(words)
        for i in range(len(text)):
            for j in range(i, len(text)):
                if text[i:j+1] in words:
                    result.append([i, j])
        return result

Time complexity: O(n^2)
Space complexity: O(n)