Majority Element

Majority Element

 

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

这道题我没有看提示，直接用hash表，遍历数组，将出现的次数保存到hash表中，最后遍历hash表，找出满足要求的元素。时间复杂度为O(n)

import java.util.Hashtable;
import java.util.Iterator;

public class Solution {
    public int majorityElement(int[] num) {
        Hashtable<Integer, Integer> hashtable = new Hashtable<Integer, Integer>();
        int result = 0;
        
        for(int i = 0; i < num.length; i++){
            Integer times = hashtable.get(num[i]);
            if(times == null)
                hashtable.put(num[i], 1);
            else{
                times = times + 1;
                hashtable.put(num[i], times);
            }
        }//for
        //遍历hash表
        Iterator<Integer> it = hashtable.keySet().iterator();
        while(it.hasNext()){
            int key = it.next();
            if(hashtable.get(key) > num.length / 2){
                result = key;
                break;
            }
        }
        
        return result;
    }
}