702-search-in-a-sorted-array-of-unknown-size
Given an integer array sorted in ascending order, write a function to searchtarget
innums
. Iftarget
exists, then return its index, otherwise return-1
.However, the array size is unknown to you. You may only access the array using anArrayReader
interface, where ArrayReader.get(k)
returns the element of the array at indexk
(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 return2147483647
.
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:
- 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].
public int search(ArrayReader reader, int target) { int right = 0, val = reader.get(right); while (val != Integer.MAX_VALUE) { if (val < target) { right = right == 0 ? 1 : right * 2; val = reader.get(right); } else { break; } } int left = right / 2, mid; while (left <= right) { mid = left + (right - left) / 2; val = reader.get(mid); if (val == target) { return mid; } else if (val < target) { left = mid + 1; } else { right = mid - 1; } } return -1; }
what if we don't know the size of array(the search range)?
we will find an approximate one, by double the right index every time untile arr[right] > target
Then do a regular bs