# 0702. Search in a Sorted Array of Unknown Size

<https://leetcode.com/problems/search-in-a-sorted-array-of-unknown-size>

## Description

This is an ***interactive problem***.

You have a sorted array of **unique** elements and an **unknown size**. You do not have an access to the array but you can use the `ArrayReader` interface to access it. You can call `ArrayReader.get(i)` that:

* returns the value at the `ith` index (**0-indexed**) of the secret array (i.e., `secret[i]`), or
* returns `231 - 1` if the `i` is out of the boundary of the array.

You are also given an integer `target`.

Return the index `k` of the hidden array where `secret[k] == target` or return `-1` otherwise.

You must write an algorithm with `O(log n)` runtime complexity.

**Example 1:**

```
**Input:** secret = [-1,0,3,5,9,12], target = 9
**Output:** 4
**Explanation:** 9 exists in secret and its index is 4.
```

**Example 2:**

```
**Input:** secret = [-1,0,3,5,9,12], target = 2
**Output:** -1
**Explanation:** 2 does not exist in secret so return -1.
```

**Constraints:**

* `1 <= secret.length <= 104`
* `-104 <= secret[i], target <= 104`
* `secret` is sorted in a strictly increasing order.

## ac

```java
```


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