题目：
题解：
class Solution {static final int L = 10;Map<Character, Integer> bin = new HashMap<Character, Integer>() {{put('A', 0);put('C', 1);put('G', 2);put('T', 3);}};public List<String> findRepeatedDnaSequences(String s) {List<String> ans = new ArrayList<String>();int n = s.length();if (n <= L) {return ans;}int x = 0;for (int i = 0; i < L - 1; ++i) {x = (x << 2) | bin.get(s.charAt(i));}Map<Integer, Integer> cnt = new HashMap<Integer, Integer>();for (int i = 0; i <= n - L; ++i) {x = ((x << 2) | bin.get(s.charAt(i + L - 1))) & ((1 << (L * 2)) - 1);cnt.put(x, cnt.getOrDefault(x, 0) + 1);if (cnt.get(x) == 2) {ans.add(s.substring(i, i + L));}}return ans;}
}