Complete implementation of Iterative Ternary Search in java
import static java.lang.String.format;
import java.util.Arrays;
import java.util.Random;
import java.util.stream.Stream;
import com.thealgorithms.devutils.searches.SearchAlgorithm;
/**
* A iterative version of a ternary search algorithm This is better way to
* implement the ternary search, because a recursive version adds some overhead
* to a stack. But in java the compile can transform the recursive version to
* iterative implicitly, so there are no much differences between these two
* algorithms
*
* <p>
* Worst-case performance Θ(log3(N)) Best-case performance O(1) Average
* performance Θ(log3(N)) Worst-case space complexity O(1)
*/
public class IterativeTernarySearch implements SearchAlgorithm {
@Override
public <T extends Comparable<T>> int find(T[] array, T key) {
int left = 0;
int right = array.length - 1;
while (right > left) {
int leftCmp = array[left].compareTo(key);
int rightCmp = array[right].compareTo(key);
if (leftCmp == 0) {
return left;
}
if (rightCmp == 0) {
return right;
}
int leftThird = left + (right - left) / 3 + 1;
int rightThird = right - (right - left) / 3 - 1;
if (array[leftThird].compareTo(key) <= 0) {
left = leftThird;
} else {
right = rightThird;
}
}
return -1;
}
public static void main(String[] args) {
// just generate data
Random r = new Random();
int size = 100;
int maxElement = 100000;
Integer[] integers
= Stream.generate(() -> r.nextInt(maxElement)).limit(size).sorted().toArray(Integer[]::new);
// the element that should be found
Integer shouldBeFound = integers[r.nextInt(size - 1)];
IterativeTernarySearch search = new IterativeTernarySearch();
int atIndex = search.find(integers, shouldBeFound);
System.out.println(
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));
}
}