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