1. Description

Given an 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?

2. Runtime Distribution

3. Submission Details

4. Example

Input: 14,14,14,35,23, 23,23
Ouput: 35

5. Code

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public int singleNumber(int[] nums) {
	if (nums == null || nums.length == 0) {
		return 0;
	}
	int result = 0;
	for (int k = 0; k < 32; k++) {
		int count = 0;
		for (int i = 0; i < nums.length; i++) {
			count += ((nums[i] >> k) & 1);
			count %= 3;
		}
		if (count == 1) {
			result |= (count << k);
		}
	}
	return result;
}

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6.Test

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public class LeetCode0137 {
	public int singleNumber(int[] nums) {
		if (nums == null || nums.length == 0) {
			return 0;
		}
		int result = 0;
		for (int k = 0; k < 32; k++) {
			int count = 0;
			for (int i = 0; i < nums.length; i++) {
				count += ((nums[i] >> k) & 1);
				count %= 3;
			}
			if (count == 1) {
				result |= (count << k);
			}
		}
		return result;
	}

	public static void main(String[] args) {
		int[] nums = { 1, 1, 1, 3, 3, 3, 4 };
		LeetCode0137 leetcode = new LeetCode0137();
		System.out.println(leetcode.singleNumber(nums));
	}
}

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