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;
     }
 }