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
Solution: Keep a variable to avoid boundary checking.
class Solution { public List<List<Integer>> largeGroupPositions(String S) { int left = 0, right = 0, n = S.length(); char current = 'A'; List<List<Integer> > result = new ArrayList<List<Integer> >(); while (right < n) { while (right < n && S.charAt(right) == current) { right++; } if (right - left >= 3) { List<Integer> temp = new ArrayList<>(); temp.add(left); temp.add(right - 1); result.add(temp); } left = right; right = left; if (left < n) { current = S.charAt(left); } } return result; } }