Question

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]]

Difficulty:Easy

Category:Array

Analyze

Solution

class Solution {
 public:
  vector<vector<int>> largeGroupPositions(string S) {
    int left = 0, right = 0, len = S.length();
    vector<vector<int>> res;
    while (right < len) {
      while (right < len && S[right] == S[left]) ++right;
      if (right - left >= 3) res.push_back({left, right - 1});
      left = right;
    }
    return res;
  }
};