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830. Positions of Large Groups

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

• Java
• C++
• Python
• Go

• 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;
      }
  };
  

• 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
  
  

• 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
  }
  

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