LeetCode1. 两数之和

输入：nums = [2,7,11,15], target = 9
输出：[0,1]
解释：因为 nums[0] + nums[1] == 9 ，返回 [0, 1] 。

输入：nums = [3,2,4], target = 6
输出：[1,2]

输入：nums = [3,3], target = 6
输出：[0,1]

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