Algorithm

[LeetCode 137] Single Number II [Java] [Runtime : 9MS]

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2017-08-31

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08/31

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

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;
}

6.Test

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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