Positions of Large Groups Python Solution

lcpy gen -n 830   # by problem number
lcpy gen -s positions_of_large_groups   # by problem name

Input: s = "abbxxxxzzy"
Output: [[3,6]]
Explanation: "xxxx" is the only large group with start index 3 and end index 6.

Input: s = "abc"
Output: []
Explanation: We have groups "a", "b", and "c", none of which are large groups.

Input: s = "abcdddeeeeaabbbcd"
Output: [[3,5],[6,9],[12,14]]
Explanation: The large groups are "ddd", "eeee", and "bbb".

class Solution:
    # Time: O(n)
    # Space: O(1) excluding output
    def large_group_positions(self, s: str) -> list[list[int]]:
        result: list[list[int]] = []
        start = 0
        for i in range(1, len(s) + 1):
            if i == len(s) or s[i] != s[start]:
                if i - start >= 3:
                    result.append([start, i - 1])
                start = i
        return result