# 702. Search in a Sorted Array of Unknown Size 搜索长度未知的有序数组

@TOC

## # 题目描述

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.

Example 1:

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

Example 2:

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

Note:

1. You may assume that all elements in the array are unique.
2. The value of each element in the array will be in the range [-9999, 9999].

## # 解题方法

### # 遍历

C++代码如下：

``````// Forward declaration of ArrayReader class.

class Solution {
public:
int index = 0;
return index;
index ++;
}
return -1;
}
};
``````

### # 二分查找

C++代码如下：

``````// Forward declaration of ArrayReader class.

class Solution {
public:
int left = 0;
int right = 20010;
// [left, right)
while (left < right) {
int mid = left + (right - left) / 2;
if (val == target) {
return mid;
} else if (val < target) {
left = mid + 1;
} else {
right = mid;
}
}
return -1;
}
};
``````

## # 日期

2019 年 9 月 24 日 —— 梦见回到了小学，小学已经芳草萋萋破败不堪