largeGroupPositions.go

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

package lstring

func largeGroupPositions(S string) [][]int {
	res := [][]int{}
	for i := 0; i < len(S); {
		j := i + 1
		for j < len(S) && S[j] == S[i] {
			j++
		}
		if j-i >= 3 {
			res = append(res, []int{i, j - 1})
		}
		i = j
	}
	return res
}