leetcode SingleNumberII
z
 2019-04-09 10:36:27   
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public class SingleNumberII {
  /**
   * Given a non-empty array of integers, every element appears three times except for one,
   * which appears exactly once. Find that single one.
   *
   * Note:
   *
   * Your algorithm should have a linear runtime complexity.
   * Could you implement it without using extra memory?
   *
   * Example 1:
   *
   * Input: [2,2,3,2]
   * Output: 3
   * Example 2:
   *
   * Input: [0,1,0,1,0,1,99]
   * Output: 99
   */
  public static int singleNumber(int[] nums) {
    int ans = 0;
    int mask;
    for (int i=0; i<32; i++) {
      mask = 1 << i;
      int t = 0;
      for (int n: nums) {
        t += mask & n;
      }
      if (t%3 == 1){
        ans |= mask;
      }
    }
    return ans;
  }
  public static void main(String[] args) {
    int[] test = new int[]{1,1,1,2,2,2,3,3,3,4};
    System.out.println(singleNumber(test));
  }
}