leetcode 简单 两数之和

class Solution {
    public int[] twoSum(int[] nums, int target) {
        HashMap<Integer, Integer> hashMap = new HashMap<>();
        for (int i = 0; i < nums.length; ++i) {
            // K 值 和 V下表         
            if (null != hashMap.get(target - nums[i])) {
                return new int[]{i,hashMap.get( target - nums[i])};
            } else {
                hashMap.put(nums[i], i);
            }
        }
        return new int[]{};
    }

}