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702. Search in a Sorted Array of Unknown Size

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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.

 

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].

Solutions

Python3

# """
# This is ArrayReader's API interface.
# You should not implement it, or speculate about its implementation
# """
#class ArrayReader:
#    def get(self, index: int) -> int:

class Solution:
    def search(self, reader, target):
        """
        :type reader: ArrayReader
        :type target: int
        :rtype: int
        """
        left, right = 0, 20000
        while left < right:
            mid = (left + right) >> 1
            if reader.get(mid) >= target:
                right = mid
            else:
                left = mid + 1
        return left if reader.get(left) == target else -1

Java

/**
 * // 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 = 20000;
        while (left < right) {
            int mid = left + right >> 1;
            if (reader.get(mid) >= target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return reader.get(left) == target ? left : -1;
    }
}

C++

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

class Solution {
public:
    int search(const ArrayReader& reader, int target) {
        int left = 0, right = 20000;
        while (left < right) {
            int mid = left + right >> 1;
            if (reader.get(mid) >= target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return reader.get(left) == target ? left : -1;
    }
};

Go

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

func search(reader ArrayReader, target int) int {
	left, right := 0, 20000
	for left < right {
		mid := (left + right) >> 1
		if reader.get(mid) >= target {
			right = mid
		} else {
			left = mid + 1
		}
	}
	if reader.get(left) == target {
		return left
	}
	return -1
}

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