题目：https://leetcode.cn/problems/two-sum/description/?envType=study-plan-v2&envId=top-100-liked

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