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# 187. Repeated DNA Sequences

[187. Repeated DNA Sequences](https://leetcode.com/problems/repeated-dna-sequences/)

1. 使用 Hash Table 的特性來判斷是否有重複出現的 sequence
2. 滑動窗口的方式來找

```python
class Solution:
    def findRepeatedDnaSequences(self, s: str) -> List[str]:
        table = defaultdict(int)
        for i in range(len(s) - 9):
            table[s[i:i+10]] += 1
        ans = []
        for key, val in table.items():
            if val >= 2:
                ans.append(key)
        return ans
```