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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

  • 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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