LeetCode 1. 两数之和

题目连接：https://leetcode-cn.com/problems/two-sum/
Java解法：

   public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> used = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            int com = target - nums[i];
            if (used.containsKey(com) && used.get(com) != i) {
                return new int[]{used.get(com), i};
            }
            used.put(nums[i], i);
        }
        return new int[0];
    }