Majority Number III

 1 public class Solution {
 2     /**
 3      * @param nums: A list of integers
 4      * @param k: As described
 5      * @return: The majority number
 6      */
 7     public int majorityNumber(ArrayList<Integer> nums, int k) {
 8         if(nums == null || nums.size() == 0) {
 9             return Integer.MIN_VALUE;
10         }
11         
12         //most k - 1 values in the map
13         HashMap<Integer, Integer> counters = new HashMap<Integer, Integer>();
14         for(int num : nums) {
15             if(counters.containsKey(num)) {
16                 counters.put(num, counters.get(num) + 1);
17             }else {
18                 if(counters.size() < k - 1) {
19                     counters.put(num, 1);
20                 }else {
21                     update(counters);
22                 }
23             }
24         }
25         
26         //corner case
27         if(counters.size() == 0) {
28             return Integer.MIN_VALUE;
29         }
30         
31         //clear count
32         for(int key : counters.keySet()) {
33             counters.put(key, 0);
34         }
35         
36         //recalculate the counter
37         for(int num : nums) {
38             if(counters.containsKey(num)) {
39                 counters.put(num, counters.get(num) + 1);
40             }
41         }
42         
43         int result = 0, maxCount = Integer.MIN_VALUE;
44         for(int key : counters.keySet()) {
45             int count = counters.get(key);
46             if(count > maxCount) {
47                 result = key;
48                 maxCount = count;
49             }
50         }
51         
52         return result;
53     }
54     
55     private void update(HashMap<Integer, Integer> counters) {
56         ArrayList<Integer> removeList = new ArrayList<Integer>();
57         for(int key : counters.keySet()) {
58             counters.put(key, counters.get(key) - 1);
59             if(counters.get(key) == 0) {
60                 removeList.add(key);
61             }
62         }
63         
64         for(int key : removeList) {
65             counters.remove(key);
66         }
67     }
68 }