[LeetCode]229. Majority Element II

Problem Description

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.

[]https://leetcode.com/problems/majority-element-ii/]

思路

摩尔投票法。

先利用投票法选出获得”票数“最多的两个数，在判断这两个数是否符合要求。

Code

package q229;

import java.util.ArrayList;
import java.util.List;

public class Solution {

public static List<Integer> majorityElement(int[] nums) {
List<Integer> ans=new ArrayList<Integer>();
if(nums.length<1) return ans;
int a=0,b=0;
int atime=0,btime=0;

for(int i=0;i<nums.length;i++){
if(nums[i]==a) atime++;
else if(nums[i]==b) btime++;
else if(atime==0){
a=nums[i];
atime=1;
}
else if(btime==0){
b=nums[i];
btime=1;
}
else{
atime--;
btime--;
}
}
atime=0;
btime=0;
for(int i=0;i<nums.length;i++){
if(nums[i]==a) atime++;
else if(nums[i]==b) btime++;
}

if(atime>nums.length/3) ans.add(a);
if(btime>nums.length/3) ans.add(b);

return ans;
}
public static void main(String[] args) {
int[] a={1,2};
System.out.print(majorityElement(a).toString());
}

}