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;
     }
 }