class Solution {
public int[] twoSum(int[] nums, int target) {
if(nums == null || nums.length == 0) {
return new int[0];
}
HashMap<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];
}
}