# Find intersection between Two Sorted Arrays.

Objective: Given two sorted arrays, Find intersection point between them.

Examples:

```int[] a = { 1, 2, 3, 6, 8, 10 };
int[] b = { 4, 5, 6, 11, 15, 20 };
Output: Intersection point is : 6
```

Approach:

Naive Approach: Use 2 loops and compare each elements in both array and as soon as you find the intersection point, return it. Time Complexity – O(n2).

Better Approach: Time Complexity – O(n)

• Say Arrays are arrA[] and arrB[] and indexes for navigation are x and y respectively.
• Since arrays are sorted, compare the first element of both the arrays.(x=0, y=0)
• If both elements are same, we have our intersection point, return it.
• Else if element of arrA[x] > element of arrB[y], increase the arrB[] index, y++.
• Else if element of arrA[x] < element of arrB[y], increase the arrA[] index, x++.
• If any of the array gets over that means you have not found the intersection point. return -1.

Complete Code:

 public class IntersecionPoint2Arrays { int intersectionPoint = –1; int x; int y; public int intersection(int[] arrA, int[] arrB) { while (x < arrA.length && y < arrB.length) { if (arrA[x] > arrB[y]) y++; else if (arrA[x] < arrB[y]) x++; else { intersectionPoint = arrA[x]; return intersectionPoint; } } return intersectionPoint; } public static void main(String[] args) throws java.lang.Exception { int[] a = { 1, 2, 3, 6, 8, 10 }; int[] b = { 4, 5, 6, 11, 15, 20 }; IntersecionPoint2Arrays i = new IntersecionPoint2Arrays(); System.out.println("Intersection point is : " + i.intersection(a, b)); } }

Output:

```Intersection point is : 6
```