• https://leetcode-cn.com/problems/two-sum/
      1. public int[] twoSum(int[] nums, int target) {
      2.    Map<Integer, Integer> map = new HashMap<>();
      3.    for (int i = 0; i < nums.length; i++) {
      4.        if (map.containsKey(target - nums[i])) {
      5.            return new int[]{map.get(target - nums[i]), i};
      6.        }
      7.        map.put(nums[i], i);
      8.    }
      9.    return new int[]{-1, -1};
      10. }