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# Algorithm
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For Q10, you want to create a new array with appropriate length in the beginning of the function.
### Optional Question
#### OQ1: findLongestSubarray
Write a function **`int findLongestSubarray(int[] arr)`** that takes in an array of integers and returns the length of the longest subarray in which the numbers are in ascending order. For example, if the input array is {2, 6, 4, 8, 10, 15}, the function should return 4, because the longest subarray in which the numbers are in ascending order is {4, 8, 10, 15}.
Sample Code is below:
```java
public class Main {
public static int findLongestSubarray(int[] arr) {
// Your code here
}
public static void main(String[] args) {
// Test the function with different input arrays
int[] array = {2, 6, 4, 8, 10, 15};
System.out.println(findLongestSubarray(array));// should return 4
}
}
```
#### OQ2: findFirstDuplicate
Implement a function **int findFirstDuplicate(int\[] arr)** that takes in an array of integers and returns the first duplicate number in the array. If there are no duplicate numbers, the function should return -1.
For example, if the input array is {2, 3, 1, 5, 2, 4}, the function should return 2, because 2 is the first duplicate number in the array.
Sample Code is below:
```java
public class Main {
public static int findFirstDuplicate(int[] arr) {
// Your code here
}
public static void main(String[] args) {
// Test the function with different input arrays
int[] arr1 = {2, 3, 1, 5, 2, 4};
int[] arr2 = {1, 2, 3, 4, 5};
int[] arr3 = {5, 3, 2, 5, 1, 4};
System.out.println(findFirstDuplicate(arr1)); // should return 2
System.out.println(findFirstDuplicate(arr2)); // should return -1
System.out.println(findFirstDuplicate(arr3)); // should return 5
}
}
```