Question

830. Positions of Large Groups

中文文档

Description

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.

Solutions

Solution 1

class Solution:
  def largeGroupPositions(self, s: str) -> List[List[int]]:
    i, n = 0, len(s)
    ans = []
    while i < n:
      j = i
      while j < n and s[j] == s[i]:
        j += 1
      if j - i >= 3:
        ans.append([i, j - 1])
      i = j
    return ans

class Solution {
  public List<List<Integer>> largeGroupPositions(String s) {
    int n = s.length();
    int i = 0;
    List<List<Integer>> ans = new ArrayList<>();
    while (i < n) {
      int j = i;
      while (j < n && s.charAt(j) == s.charAt(i)) {
        ++j;
      }
      if (j - i >= 3) {
        ans.add(Arrays.asList(i, j - 1));
      }
      i = j;
    }
    return ans;
  }
}

class Solution {
public:
  vector<vector<int>> largeGroupPositions(string s) {
    int n = s.size();
    int i = 0;
    vector<vector<int>> ans;
    while (i < n) {
      int j = i;
      while (j < n && s[j] == s[i]) {
        ++j;
      }
      if (j - i >= 3) {
        ans.push_back({i, j - 1});
      }
      i = j;
    }
    return ans;
  }
};

func largeGroupPositions(s string) [][]int {
  i, n := 0, len(s)
  ans := [][]int{}
  for i < n {
    j := i
    for j < n && s[j] == s[i] {
      j++
    }
    if j-i >= 3 {
      ans = append(ans, []int{i, j - 1})
    }
    i = j
  }
  return ans
}