题目：
题解：
const L = 10
var bin = map[byte]int{'A': 0, 'C': 1, 'G': 2, 'T': 3}
func findRepeatedDnaSequences(s string) (ans []string) {
n := len(s)
if n <= L {
return
}
x := 0
for _, ch := range s[:L-1] {
x = x<<2 | bin[byte(ch)]
}
cnt := map[int]int{}
for i := 0; i <= n-L; i++ {
x = (x<<2 | bin[s[i+L-1]]) & (1<<(L*2) - 1)
cnt[x]++
if cnt[x] == 2 {
ans = append(ans, s[i:i+L])
}
}
return ans
}