Given an array of integers, every element appears three times except for one. Find that single one. Note: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?
1 /**
2 *
3 */
4 package solution;
5
6 import java.util.Arrays;
7
8 /**
9 * @author whh
10 *
11 * Given an array of integers, every element appears three times except
12 * for one. Find that single one.
13 *
14 * Note: Your algorithm should have a linear runtime complexity. Could
15 * you implement it without using extra memory?
16 */
17 public class SingleNumber2 {
18
19 /**
20 * @param args
21 */
22 public static void main(String[] args) {
23 int[] A1 = { 1 };
24 int[] A2 = { 1, 2, 3, 4, 1, 2, 3, 1, 2, 3 };
25 int[] A3 = { 1, 1, 2, 4, 2, 4, 3, 5, 3, 1, 2, 3, 4 };
26 int[] A4 = { 1, 1 };
27 int[] A5 = { 1, 1, 1, 2, 2, 2, 3, 3 };
28 System.out.println(singleNumber(A1));
29 System.out.println(singleNumber(A2));
30 System.out.println(singleNumber(A3));
31 System.out.println(singleNumber(A4));
32 System.out.println(singleNumber(A5));
33 }
34
35 /**
36 *
37 * @param A
38 * @return
39 */
40 public static int singleNumber(int[] A) {
41 Arrays.sort(A);
42 int ret = 0;
43 for (int i = 0; i < A.length; i = i + 3) {
44 if (i == A.length - 1 || i == A.length - 2) {
45 ret = A[i];
46 break;
47 } else if (!(A[i] == A[i + 1] && A[i] == A[i + 2])) {
48 ret = A[i];
49 break;
50 }
51 }
52 return ret;
53 }
54
55 }
