lintcode-medium-Majority Number II

Given an array of integers, the majority number is the number that occursmore than 1/3 of the size of the array.

Find it.

 

 Notice

There is only one majority number in the array.

Example

Given [1, 2, 1, 2, 1, 3, 3], return 1.

Challenge

O(n) time and O(1) extra space.

 

public class Solution {
    /**
     * @param nums: A list of integers
     * @return: The majority number that occurs more than 1/3
     */
    public int majorityNumber(ArrayList<Integer> nums) {
        // write your code
        
        if(nums == null || nums.size() == 0)    
            return 0;
        
        Integer num1 = null;
        Integer num2 = null;
        int count1 = 0;
        int count2 = 0;
        
        for(int i = 0; i < nums.size(); i++){
            int temp = nums.get(i);
            
            if(num1 == null){
                num1 = temp;
                count1 = 1;
            }
            else if(num1 == temp){
                count1++;
            }
            else if(num2 == null){
                num2 = temp;
                count2 = 1;
            }
            else if(num2 == temp){
                count2++;
            }
            else{
                count1--;
                count2--;
                if(count1 == 0){
                    num1 = temp;
                    count1 = 1;
                }
                if(count2 == 0){
                    num2 = temp;
                    count2 = 1;
                }
            }
        }
        
        count1 = 0;
        count2 = 0;
        
        for(int i = 0; i < nums.size(); i++){
            if(num1 == nums.get(i))
                count1++;
            if(num2 == nums.get(i))
                count2++;
        }
        
        if(count1 > nums.size() / 3)
            return num1;
        
        return num2;
    }
}