LeetCode:Majority Element II

Posted 2020-07-26 walker lee

Majority Element II

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Total Accepted: 30176 Total Submissions: 115847 Difficulty: Medium

Given an integer array of size n, find all elements that appear more than ? n/3 ? times. The algorithm should run in linear time and in O(1) space.

Hint:

1. How many majority elements could it possibly have?
2. Do you have a better hint? Suggest it!

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 (E) Majority Element

思路：

最多只能有两个数符合结果，因此用两个变量，计算它们是否超过? n/3 ?。

java code:

public class Solution {
    public List<Integer> majorityElement(int[] nums) {
        
        List<Integer> ans = new ArrayList<Integer>();
        if(nums == null || nums.length == 0) return ans;
        int x = 0, y = 1;
        int cx = 0, cy = 0;
        for(int num : nums) {
            
            if(num == x) {
                cx++;
            }
            else if(num == y) {
                cy++;
            }
            else if(cx == 0) {
                x = num;
                cx = 1;
            }
            else if(cy == 0) {
                y = num;
                cy = 1;
            }
            else {
                cx--;
                cy--;
            }
        }
        cx = cy = 0;
        for(int num : nums) {
            if(num == x) cx++;
            else if(num == y) cy++;
        }
        if(cx > nums.length/3) ans.add(x);
        if(cy > nums.length/3) ans.add(y);
        
        return ans;
    }
}