[LeetCode] Problem 229 - Majority Element II

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Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times.

Note

The algorithm should run in linear time and in O(1) space.

Example

No.1

Input: [3,2,3]

Output: [3]

No.2

Input: [1,1,1,3,3,2,2,2]

Output: [1,2]

Code

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public List<Integer> majorityElement(int[] nums) {
    List<Integer> result = new ArrayList<>();
    int candidate1 = 0;
    int candidate2 = 0;
    int count1 = 0;
    int count2 = 0;

    for (int num : nums) {
        if (num == candidate1)
            count1++;
        else if (num == candidate2)
            count2++;
        else if (count1 == 0) {
            count1 = 1;
            candidate1 = num;
        }
        else if (count2 == 0) {
            count2 = 1;
            candidate2 = num;
        }
        else {
            count1--;
            count2--;
        }
    }

    count1 = 0;
    count2 = 0;

    for (int num : nums) {
        if (num == candidate1)
            count1++;
        else if (num == candidate2)
            count2++;
    }

    if (count1 > nums.length / 3)
        result.add(candidate1);
    if (count2 > nums.length / 3)
        result.add(candidate2);

    return result;
}