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# 702. Search in a Sorted Array of Unknown Size

### Description

Given an integer array sorted in ascending order, write a function to search `target` in `nums`.  If `target` exists, then return its index, otherwise return `-1`. **However, the array size is unknown to you**. You may only access the array using an `ArrayReader` interface, where `ArrayReader.get(k)` returns the element of the array at index `k` (0-indexed).

You may assume all integers in the array are less than `10000`, and if you access the array out of bounds, `ArrayReader.get` will return `2147483647`.

### Constraints

* You may assume that all elements in the array are unique.
* The value of each element in the array will be in the range `[-9999, 9999]`.
* The length of the array will be in the range `[1, 10^4]`.

### Approach

### Links

* GeeksforGeeks
* [Leetcode](https://leetcode.com/problems/search-in-a-sorted-array-of-unknown-size/)
* ProgramCreek
* YouTube

### **Examples**

{% tabs %}
{% tab title="Example 1" %}
**Input:** array = \[-1, 0, 3, 5, 9, 12], target = 9

**Output:** 4

**Explanation:** 9 exists in nums and its index is 4
{% endtab %}

{% tab title="Example 2" %}
**Input:** array = \[-1, 0, 3, 5, 9, 12], target = 2

**Output:** -1

**Explanation:** 2 does not exist in nums so return -1
{% endtab %}
{% endtabs %}

### **Solutions**

{% tabs %}
{% tab title="Solution 1" %}

```java
/**
 * Time complexity : 
 * Space complexity : 
 */

/**
 * // This is ArrayReader's API interface.
 * // You should not implement it, or speculate about its implementation
 * interface ArrayReader {
 *     public int get(int index) {}
 * }
 */

class Solution {
    public int search(ArrayReader reader, int target) {
        int low = 0, high = Integer.MAX_VALUE;
        while(low <= high) {
            int mid = low + (high-low)/2;
            int val = reader.get(mid);
            if(val == target) {
                return mid;
            } else if(val < target) {
                low = mid + 1;
            } else {
                high = mid - 1;
            }
        }
        
        return -1;
    }
}
```

{% endtab %}

{% tab title="Solution 2" %}

```java
/**
 * Time complexity : 
 * Space complexity : 
 */

/**
 * // This is ArrayReader's API interface.
 * // You should not implement it, or speculate about its implementation
 * interface ArrayReader {
 *     public int get(int index) {}
 * }
 */

class Solution {
    public int search(ArrayReader reader, int target) {
        int high = 1;
        while(reader.get(high) < target) {
            high *= 2;
        }
        
        int low = high / 2;
        
        while(low <= high) {
            int mid = low + (high-low)/2;
            int val = reader.get(mid);
            if(val == target) {
                return mid;
            } else if(val < target) {
                low = mid+1;
            } else {
                high = mid-1;
            }
        }
        return -1;
    }
}
```

{% endtab %}
{% endtabs %}

### **Follow up**

*