[LeetCode] 830. Positions of Large Groups_Easy tag: Two Pointers
2018-08-20 03:56 Johnson_强生仔仔 阅读(183) 评论(0) 编辑 收藏 举报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
思路用两个pointers
Code
class Solution: def largeGroupPositions(self, s): l, r, lr, ans = 0, 0, len(s),[] while r < lr: if s[r] != s[l]: if (r - l) >= 3: ans.append([l, r-1]) l = r elif r == lr -1 and r - l + 1 >= 3: ans.append([l,r]) r += 1 return ans