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
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].
Solution:
/**
* // 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 left = 0, right = 1;
while (reader.get(right) < target) {
right *= 2;
}
while (left <= right) {
int mid = (left + right) / 2;
if (reader.get(mid) == target) {
return mid;
} else if (reader.get(mid) < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
return -1;
}
}