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 <= 1000
-
s
contains lowercase English letters only.
SOLUTION:
class Solution:
def largeGroupPositions(self, s: str) -> List[List[int]]:
n = len(s)
i = 0
op = []
while i < n:
ctr = 1
while i < n - 1 and s[i] == s[i + 1]:
ctr += 1
i += 1
i += 1
if ctr >= 3:
op.append([i - ctr, i - 1])
return op
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