[leetcode]Repeated DNA Sequences

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public class Solution { public List<String> findRepeatedDnaSequences(String s) { List<String> result = new ArrayList<String>(); HashMap<Integer, Integer> lookup = new HashMap<Integer, Integer>(); String current = ""; int sum = 0; for (int i = 0; i < s.length(); i++){ sum = ((sum << 2)+getMap(s.charAt(i))) & 0xFFFFF; current += s.charAt(i); if (current.length() == 10){ if (lookup.containsKey(sum)){ if (lookup.get(sum) == 1){ result.add(current); lookup.put(sum,2); } }else{ lookup.put(sum,1); } current = current.substring(1,10); } } return result; } int getMap(char a){ if (a == 'A') return 0; if (a == 'C') return 1; if (a == 'G') return 2; return 3; } }