169. Majority Element

题目：

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

链接： http://leetcode.com/problems/majority-element/

2/20/2017, Java

performance不好，为什么？

public class Solution {
    public int majorityElement(int[] nums) {
        HashMap<Integer, Integer> dict = new HashMap<Integer, Integer>();
        int count = 0;
        if (nums.length == 1) return nums[0];

        for(int i = 0; i < nums.length; i++) {
            if (dict.containsKey(nums[i])) {
                count = dict.get(nums[i]);
                if (count + 1 > nums.length / 2) return nums[i];
                dict.put(nums[i], count + 1);
            } else {
                dict.put(nums[i], 1);
            }
        }
        return 0;
    }
}

因为有Boyer-Moore Majority vote algorithm!

留给二刷，并且要学会多于特定比例的情况。