Skip to content

Added Interpolation Search and JUnit test. #647

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Dec 4, 2018
Merged

Added Interpolation Search and JUnit test. #647

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
60 changes: 60 additions & 0 deletions src/main/java/com/search/InterpolationSearch.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,60 @@
package src.main.java.com.search;

public class InterpolationSearch {

/**
* A linear interpolation search algorithm that finds the position of a
* target value in an sorted array using its lowest value and highest value.
*
* Average time-complexity O(log log n) - uniformly distributed.
* Worst-case time-complexity O(n) - non-uniformly distributed
* Worst-case space complexity O(1)
*
* @param <T>This is any comparable type
* @param arr This is the array where the element should be found
* @param key This is the element to find in the array
* @return The index of the key in the array
*/
public <T extends Comparable<T>> int findIndex(T arr[], T key) {
return checkCondition(arr, key, 0, arr.length - 1);
}

/**
* @param lowIndex The first and smallest element in the sorted array
* @param highIndex The last and largest element in the sorted array
* @return The found key's index in the array through iteration
*/
private <T extends Comparable<T>> int checkCondition(T arr[], T key, int lowIndex, int highIndex) {
boolean conditionOne = lowIndex <= highIndex && key.compareTo(arr[lowIndex]) >= 0;
boolean conditionTwo = key.compareTo(arr[lowIndex]) == 0 && key.compareTo(arr[highIndex]) <= 0;
while (conditionOne || conditionTwo) {
int position = getPostion(arr, key, lowIndex, highIndex);
if (arr[position].equals(key))
return position;

if (arr[position].compareTo(key) < 0)
lowIndex = position + 1;
else
highIndex = position - 1;
}
return -1;
}

/**
* @return The array's current retrieved index position
*/
private <T> int getPostion(T arr[], T key, int lowIndex, int highIndex) {
String startValueString = arr[lowIndex].toString(); //First convert <T> array element to String
int startValueInt = Integer.parseInt(startValueString); //Convert String to int to computate later
String endValueString = arr[highIndex].toString();
int endValueInt = Integer.parseInt(endValueString);
String keyValueString = key.toString(); //Repeat for <T> key to later computate
int keyValueInt = Integer.parseInt(keyValueString);

int arrayIndexRangeDiff = highIndex - lowIndex;
int arrayHighLowValuesDiff = endValueInt - startValueInt;
int keyMinusArrayLowValue = keyValueInt - startValueInt;
int position = lowIndex + (((arrayIndexRangeDiff) / (arrayHighLowValuesDiff) * (keyMinusArrayLowValue)));
return position;
}
}
29 changes: 29 additions & 0 deletions src/test/java/com/search/InterpolationSearchTest.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
package src.test.java.com.search;

import org.junit.Assert;
import org.junit.Test;

import src.main.java.com.search.InterpolationSearch;

public class InterpolationSearchTest {

@Test
public void testInterpolationSearch() {
InterpolationSearch interpolationSearch = new InterpolationSearch();

Integer arr[] = {10, 12, 13, 16, 18, 19, 21};
int x = 18;
int index = interpolationSearch.findIndex(arr, x);
Assert.assertEquals("Incorrect index", 4, index);

Integer arrTwo[] = {-210, -190, -180, -160, -130, -120, -100};
x = -190;
index = interpolationSearch.findIndex(arrTwo, x);
Assert.assertEquals("Incorrect index", 1, index);

String arrString[] = {"10", "12", "13", "16", "22", "25","29"};
String stringX = "13";
index = interpolationSearch.findIndex(arrString, stringX);
Assert.assertEquals("Incorrect index", 2, index);
}
}