Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
```
private static int[] getTargetArray(int[] arr, int target) {
if (arr == null || arr.length == 0) return null;
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
int index1 = 0;
int index2 = 0;
for (int i = 0; i < arr.length; i++) {
if (map.containsKey(target - arr[i])) {
index1 = map.get(target - arr[i]);
index2 = i;
int[] targetArr = {index1,index2};
return targetArr;
} else {
map.put(arr[i], i);
}
}
return null;
```
