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137. Single Number II

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

思路分析

由于除了唯一数外,其余数字都出现了三次,那么将每个数字的每位相加,除以 3,余数即为唯一数。

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/**
 * @author D瓜哥 · https://www.diguage.com
 * @since 2024-09-19 14:48:40
 */
public int singleNumber(int[] nums) {
  int[] bits = new int[32];
  for (int i = 0; i < 32; i++) {
    int cnt = 0;
    for (int j = 0; j < nums.length; j++) {
      int num = nums[j];
      cnt += (num & 1);
      nums[j] = (num >>> 1);
    }
    bits[i] = cnt % 3;
  }
  int result = 0;
  for (int i = 31; i >= 0; i--) {
    result <<= 1;
    result |= bits[i];
  }
  return result;
}