169. Majority Element

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.

1.  首先用hashmap

hashmap中先写   !map.containsKey() 比 map.containsKey() 的速度快一倍

if(nums.length == 0 && nums == null) return 0;                    Map<Integer,Integer> map = new HashMap<>();        for(int i = 0; i < nums.length; i++) {            if(!map.containsKey(nums[i])) {                map.put(nums[i], 1);            } else {                map.put(nums[i], map.get(nums[i]) + 1);            }        }        int c= 0;        for(Map.Entry<Integer, Integer> entry : map.entrySet()) {            if(entry.getValue() > (nums.length/2) ) c = entry.getKey();        }        return c;