Leetcode Two Sum (java)

class Solution {
    public int[] twoSum(int[] nums, int target) {
        for (int i = 0; i < nums.length; i++) {
            for (int j = i + 1; j < nums.length; j++) {
                if( nums[i] + nums[j] == target ){
                    int[] result = new int[2];
                    result[0] = i;
                    result[1] = j;
                    return result;
                }
            }
        }
        return null;
    }
}

class Solution {
    public int[] twoSum(int[] nums, int target) {
        Hashtable<Integer,Integer> map = new Hashtable<Integer,Integer>();
        for (int i = 0; i < nums.length; i++) {
            map.put(nums[i],i);
        }
        for (int i = 0; i < nums.length; i++) {
            int another = target - nums[i];
　　　　　　　//过滤元素本身
            if( map.get(another) != null &&map.get(another) > i ){
                int[] result = new int[2];
                result[0] = i;
                result[1] = map.get(another);
                return result;
            }
        }
        return null;
    }
}