Without HashMap, just have two pointers, A points to index 0, B points to index len - 1, shrink the scope based on the value and target comparison.

```
public int[] twoSum(int[] num, int target) {
int[] indice = new int[2];
if (num == null || num.length < 2) return indice;
int left = 0, right = num.length - 1;
while (left < right) {
int v = num[left] + num[right];
if (v == target) {
indice[0] = left + 1;
indice[1] = right + 1;
break;
} else if (v > target) {
right --;
} else {
left ++;
}
}
return indice;
}
```