Leetcode 给定一个数组，给定一个数字。返回数组中可以相加得到指定数字的两个索引

  
    public int[] testTwoSum(int[] nums, int target) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            int complement = target - nums[i];
            if (map.containsKey(complement)) {
                return new int[] { map.get(complement), i };
            }
            map.put(nums[i], i);
        }
        throw new IllegalArgumentException("No two sum solution");
    }
 
 
    @Test
    public void test4(){
        int[] nums = {2, 7, 11, 15};
        int target = 9;
        int[] j = testTwoSum(nums, target);
        System.out.println(Arrays.toString(j));
    }