【LeetCode】830. Positions of Large Groups 较大分组的位置（Easy）（JAVA）
题目地址: https://leetcode.com/problems/positions-of-large-groups/
题目描述：
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".
Example 4:
Input: s = "aba"
Output: []
Constraints:
- 1 <= s.length <= 1000
- s contains lower-case English letters only.
题目大意
在一个由小写字母构成的字符串 s 中，包含由一些连续的相同字符所构成的分组。
例如，在字符串 s = “abbxxxxzyy” 中，就含有 “a”, “bb”, “xxxx”, “z” 和 “yy” 这样的一些分组。
分组可以用区间 [start, end] 表示，其中 start 和 end 分别表示该分组的起始和终止位置的下标。上例中的 “xxxx” 分组用区间表示为 [3,6] 。
我们称所有包含大于或等于三个连续字符的分组为 较大分组 。
找到每一个 较大分组 的区间，按起始位置下标递增顺序排序后，返回结果。
解题方法
- 先定位一个不一样的 char 值，然后往后寻找，直到和当前 char 值不同为止
- 如果结束的位置和开始的位置个数相差大于等于 3, 就把结果保存下来
class Solution {
public List<List<Integer>> largeGroupPositions(String s) {
List<List<Integer>> list = new ArrayList<>();
for (int i = 0; i < s.length(); i++) {
char cur = s.charAt(i);
int end = i + 1;
while (end < s.length() && s.charAt(end) == cur) {
end++;
}
if (end - i >= 3) {
List<Integer> temp = new ArrayList<>();
temp.add(i);
temp.add(end - 1);
list.add(temp);
}
i = end - 1;
}
return list;
}
}
执行耗时:1 ms,击败了100.00% 的Java用户
内存消耗:38.6 MB,击败了68.86% 的Java用户
