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:

 1 public class Solution {
 2     /**
 3      * @param nums: a list of integers
 4      * @return: find a  majority number
 5      */
 6     public int majorityNumber(ArrayList<Integer> nums) {
 7         if (nums==null || nums.size()==0) return -1;
 8         int len = nums.size();
 9
10         int cur = nums.get(0);
11         int count = 1;
12         for (int i=1;i<len;i++){
13             if (cur!=nums.get(i)){
14                 count--;
15                 if (count==0){
16                     cur = nums.get(i);
17                     count=1;
18                 }
19             } else {
20                 count++;
21             }
22         }
23
24         return cur;
25     }
26 }