# 31: Find array duplicates

Given an `array`

of integers, from `1`

to `array.Length`

inclusive. Some array items appear `twice`

and others appear `once`

. Find all duplicates. The result should be in `ascending order`

Note: Solve without extra space and in

`O(n)`

runtime

`Example 1`

```
Input: [3, 2, 1, 3]
Output: [3]
```

`Example 2`

```
Input: [3, 2, 1, 3, 2]
Output: [2, 3]
```