830. 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".

A group is identified by an interval [start, end], where start and end denote the start and end indices (inclusive) of the group. In the above example, "xxxx" has the interval [3,6].

A group is considered large if it has 3 or more characters.

Return the intervals of every large group sorted in increasing order by start index.

Example 1:

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

Example 2:

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

Example 3:

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

Example 4:

Input: s = "aba"
Output: []

Constraints:

• 1 <= s.length <= 1000
• s contains lower-case English letters only.

# @lc code=start
using LeetCode

function large_group_positions(s::String)::Vector{Vector{Int}}
    ch = s[1]
    bg = 1
    res = Vector{Int}[]
    for i in 2:length(s)
        if s[i] != ch
            if i - bg > 2
                push!(res, [bg - 1, i - 2]) #1-index to 0-index
            end
            ch = s[i]
            bg = i
        end
    end
    res
end
# @lc code=end

large_group_positions (generic function with 1 method)

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