187. Repeated DNA sequence

subject ：

Answer key ：
It is stated in the question that the length is 10. Therefore, the idea of sliding window can be used to solve this problem .

First, you can maintain a length of 10 The window of is used to intercept strings , Then for the string in the window , It is necessary to judge whether there has been , If it only appears before, add it to the result list , Cycle through the window , Finally, the result list can be de duplicated .

For the above mentioned , How to judge whether a string has appeared , have access to map Data structure , Each occurrence corresponds to the string key Of value value +1

If you use Java To write this question , You can use set Data structure of , Initialize two set, Move the window once at a time , Judge whether the intercepted string is in the first set in , If in the first set in , Then add it to the second set. Otherwise, only add it to the first set. because set The data structure of can help us to de duplicate . and Go Language doesn't have set Such a data structure , So we used map To replace

Here are Go The language code

func findRepeatedDnaSequences(s string) []string {
    
	L := 10
	seen := make(map[string]int)
	ret := make([]string, 0)
	for start := 0; start+L-1 < len(s); start++ {
    
		curStr := s[start : start+L]
        if seen[curStr] == 1 {
    
            ret = append(ret, curStr)
        }
		seen[curStr]++
	}
	return ret
}