Majority Number III

Given an array of integers and a number k, the majority number is the number that occursmore than 1/k of the size of the array.

Find it.

Example

Given [3,1,2,3,2,3,3,4,4,4] and k=3, return 3.

Note

There is only one majority number in the array.

Challenge

O(n) time and O(k) extra space

对于1/k 的数，每当要删除的时候，要把k的数字同时删掉，这样不会影响最终的结果。 

public class Solution {
    /**
     * @param nums: A list of integers
     * @param k: As described
     * @return: The majority number
     */
    public int majorityNumber(ArrayList<Integer> nums, int k) {
        // write your code
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        for(int i = 0; i < nums.size(); i ++){
            int num = nums.get(i);
            if(map.containsKey(num)){
                map.put(num, map.get(num) + 1);
            }else{
                if(map.size() < 3){
                    map.put(num, 1);
                }else{//decrease every count by one, remove pair which count is 0
                    ArrayList<Integer> removeKey = new ArrayList<Integer>();
                    for (Map.Entry en : map.entrySet()){
                        en.setValue((int)en.getValue() - 1);
                        if((int)en.getValue() == 0){
                            removeKey.add((int)en.getKey());
                        }
                    }
                    for(int j = 0; j < removeKey.size(); j ++){
                        map.remove(removeKey.get(j));
                    }
                }
            }
        }
        
        int result = 0;
        int resultValue = 0;
        for (Map.Entry cur : map.entrySet()){
            if((int)cur.getValue() > resultValue){
                result = (int)cur.getKey();
                resultValue = (int)cur.getValue();
            }
        }
        return result;
    }
}