LintCode-Majority Number

Given an array of integers, the majority number is the number that occurs more than half of the size of the array. Find it.

Example

For [1, 1, 1, 1, 2, 2, 2], return 1

Challenge

O(n) time and O(1) space

Solution:

public class Solution {
    /**
     * @param nums: a list of integers
     * @return: find a  majority number
     */
    public int majorityNumber(ArrayList<Integer> nums) {
        if (nums==null || nums.size()==0) return -1;
        int len = nums.size();

        int cur = nums.get(0);
        int count = 1;
        for (int i=1;i<len;i++){
            if (cur!=nums.get(i)){
                count--;
                if (count==0){
                    cur = nums.get(i);
                    count=1;
                }
            } else {
                count++;
            }
        }

        return cur;
    }
}