# 830.Position of Large Groups

**830. Position of Large Groups**

> 题目难度 Easy

> 在一个由小写字母构成的字符串 S 中，包含由一些连续的相同字符所构成的分组。 例如，在字符串 S = "abbxxxxzyy" 中，就含有 "a", "bb", "xxxx", "z" 和 "yy" 这样的一些分组。 我们称所有包含大于或等于三个连续字符的分组为较大分组。找到每一个较大分组的起始和终止位置。 最终结果按照字典顺序输出。

```
示例 1:
输入: "abbxxxxzzy"
输出: [[3,6]]
解释: "xxxx" 是一个起始于 3 且终止于 6 的较大分组。
示例 2:
输入: "abc"
输出: []
解释: "a","b" 和 "c" 均不是符合要求的较大分组。
示例 3:
输入: "abcdddeeeeaabbbcd"
输出: [[3,5],[6,9],[12,14]]
说明:  1 <= S.length <= 1000
```

方法: 比较简单，直接遍历一遍string，然后如果有两个相同，继续向后找，最后遇到不同的，求出长度，如果大于3，则压入向量中。

```
class Solution {
public:
    vector<vector<int>> largeGroupPositions(string S) {
        vector<vector<int>> result;
        size_t len=S.length();
        for(int i=0;i<len-1;i++)
        {
            if(S[i] == S[i+1])
            {
                int x=i++,y=x;
                while(S[i] ==S[i+1] && i<len-1)
                {
                    y=++i;
                }
                if(y-x >=2)
                {
                    vector<int > tmp;
                    tmp.push_back(x);
                    tmp.push_back(y);
                    result.push_back(tmp);
            }
            }

        }
        return result;


    }
};
```


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