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  • 830. Positions of Large Groups

    1. Question:

    830. Positions of Large Groups

    url https://leetcode.com/problems/positions-of-large-groups/

    In a string S of lowercase letters, these letters form consecutive groups of the same character.

    For example, a string like S = "abbxxxxzyy" has the groups "a""bb""xxxx""z" and "yy".

    Call a group large if it has 3 or more characters.  We would like the starting and ending positions of every large group.

    The final answer should be in lexicographic order.

    Example 1:

    Input: "abbxxxxzzy"
    Output: [[3,6]]
    Explanation: "xxxx" is the single large group with starting  3 and ending positions 6.
    

    Example 2:

    Input: "abc"
    Output: []
    Explanation: We have "a","b" and "c" but no large group.
    

    Example 3:

    Input: "abcdddeeeeaabbbcd"
    Output: [[3,5],[6,9],[12,14]]

    Note:  1 <= S.length <= 1000

    2. Solution:

    class Solution:
        def largeGroupPositions(self, S):
            """
            :type S: str
            :rtype: List[List[int]]
            """
            if S is None or len(S) < 3:
                return []
    
            re_list = []
            bf_value = S[0]
            start = 0
            end = 0
            for i in range(1, len(S)):
                if S[i] == S[i - 1]:
                    continue
                end = i - 1
                if end - start + 1 >= 3:
                    re_list.append([start, end])
                start = i
            if len(S) - start >= 3:
                re_list.append([start, len(S) - 1])
    
            return re_list

    3. Complexity Analysis

    Time Complexity : O(N)

    Space Complexity: O(1)

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  • 原文地址:https://www.cnblogs.com/ordili/p/9992215.html
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