Positions of Large Groups

Positions of Large Groups

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]]

Note:  1 <= S.length <= 1000

vector<vector<int>> largeGroupPositions(string S) {
        vector<vector<int>> res;
        for(int i = 0; i < S.length(); ){
            int j = i + 1;
            while(S[j] == S[i]){
                j++;
            }
            if(j-i >= 3){
                res.push_back({i,j-1});      //二维vector可直接插入vector
            }
            i = j;
        }
        return res;
        
    }

注意点：二维vector插入的用法。