830. Positions of Large Groups

问题：

给定字符串，返回连续相同字符子串长度>=3的始终位置集合。

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]]

解法：

参考代码：

 1 class Solution {
 2 public:
 3     vector<vector<int>> largeGroupPositions(string S) {
 4         vector<vector<int>> res;
 5         int count=0;
 6         int i;
 7         char curc;
 8         for(i=0; i<S.length(); i++){
 9             if(curc!=S[i]) {
10                 if(count>=3){
11                     res.push_back({i-count, i-1});
12                 }
13                 curc = S[i];
14                 count=0;
15             }
16             count++;
17         }
18         if(count>=3){
19             res.push_back({i-count, i-1});
20         }
21         return res;
22     }
23 };