Create an array to track the times a specific number has appeared.

- First pass, go over
`nums`

and populate`arr`

. - Second pass, found elements showed up
`0`

times or twice, those are the ones we are looking for.

Thanks,

.

```
public class Solution {
public int[] findErrorNums(int[] nums) {
int len = nums.length;
int[] arr = new int[len+1];
for(int num: nums){
arr[num]++;
}
int[] res = new int[2];
for(int i=1;i<arr.length;i++){
if(arr[i]==2)
res[0] = i;
else if(arr[i]==0)
res[1]=i;
}
return res;
}
}
```