LeetCode-in-Java
830. Positions of Large Groups
Easy
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”.
Constraints:
1 <= s.length <= 1000scontains lowercase English letters only.
Solution
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Solution {
public List<List<Integer>> largeGroupPositions(String s) {
List<List<Integer>> map = new ArrayList<>();
int i = 0;
while (i < s.length()) {
int j = i;
while (j < s.length() && s.charAt(j) == s.charAt(i)) {
j++;
}
if ((j - 1) - i + 1 >= 3) {
map.add(Arrays.asList(i, j - 1));
}
i = j;
}
return map;
}
}