80 lines
2.1 KiB
Java
80 lines
2.1 KiB
Java
|
package search;
|
||
|
|
|
||
|
|
import java.util.Arrays;
|
||
|
|
import java.util.Random;
|
||
|
|
import java.util.stream.IntStream;
|
||
|
|
|
||
|
|
import static java.lang.String.format;
|
||
|
|
|
||
|
|
/**
|
||
|
|
*
|
||
|
|
* Interpolation search algorithm implementation
|
||
|
|
*
|
||
|
|
* Worst-case performance O(n)
|
||
|
|
* Best-case performance O(1)
|
||
|
|
* Average performance O(log(log(n))) if the elements are uniformly distributed if not O(n)
|
||
|
|
* Worst-case space complexity O(1)
|
||
|
|
*
|
||
|
|
*
|
||
|
|
* @author Podshivalov Nikita (https://github.com/nikitap492)
|
||
|
|
*
|
||
|
|
*/
|
||
|
|
class InterpolationSearch {
|
||
|
|
|
||
|
|
|
||
|
|
/**
|
||
|
|
* @param array is a sorted array
|
||
|
|
* @param key is a value what shoulb be found in the array
|
||
|
|
* @return an index if the array contains the key unless -1
|
||
|
|
*/
|
||
|
|
public int find(int array[], int key) {
|
||
|
|
// Find indexes of two corners
|
||
|
|
int start = 0, end = (array.length - 1);
|
||
|
|
|
||
|
|
// Since array is sorted, an element present
|
||
|
|
// in array must be in range defined by corner
|
||
|
|
while (start <= end && key >= array[start] && key <= array[end])
|
||
|
|
{
|
||
|
|
// Probing the position with keeping
|
||
|
|
// uniform distribution in mind.
|
||
|
|
int pos = start + (((end-start) / (array[end]-array[start]))*(key - array[start]));
|
||
|
|
|
||
|
|
// Condition of target found
|
||
|
|
if (array[pos] == key)
|
||
|
|
return pos;
|
||
|
|
|
||
|
|
// If key is larger, key is in upper part
|
||
|
|
if (array[pos] < key)
|
||
|
|
start = pos + 1;
|
||
|
|
|
||
|
|
// If key is smaller, x is in lower part
|
||
|
|
else
|
||
|
|
end = pos - 1;
|
||
|
|
}
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Driver method
|
||
|
|
public static void main(String[] args) {
|
||
|
|
Random r = new Random();
|
||
|
|
int size = 100;
|
||
|
|
int maxElement = 100000;
|
||
|
|
int[] integers = IntStream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray();
|
||
|
|
|
||
|
|
|
||
|
|
//the element that should be found
|
||
|
|
Integer shouldBeFound = integers[r.nextInt(size - 1)];
|
||
|
|
|
||
|
|
InterpolationSearch search = new InterpolationSearch();
|
||
|
|
int atIndex = search.find(integers, shouldBeFound);
|
||
|
|
|
||
|
|
System.out.println(String.format("Should be found: %d. Found %d at index %d. An array length %d"
|
||
|
|
, shouldBeFound, integers[atIndex], atIndex, size));
|
||
|
|
|
||
|
|
|
||
|
|
int toCheck = Arrays.binarySearch(integers, shouldBeFound);
|
||
|
|
System.out.println(format("Found by system method at an index: %d. Is equal: %b", toCheck, toCheck == atIndex));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|