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CS-378 Find kth smallest element in union of two sorted arrays (#9812)

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* CS-378 Find the Kth Smallest Element in the Union of Two Sorted Arrays

* CS-378 Fix name of unit test

* CS-378 Update merge algorithm to operate only on two input arrays

Co-authored-by: mikr <michael.krimgen@ximedes.com>
This commit is contained in:
Maiklins
2020-08-14 17:41:36 +02:00
committed by GitHub
parent 20c14c75b8
commit 5b6c1fac98
2 changed files with 414 additions and 0 deletions
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288
algorithms-searching/src/test/java/com/baeldung/algorithms/kthsmallest/KthSmallestUnitTest.java Normal file
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package com.baeldung.algorithms.kthsmallest;
import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.function.Executable;
import java.util.*;
import static com.baeldung.algorithms.kthsmallest.KthSmallest.*;
import static org.junit.jupiter.api.Assertions.*;
public class KthSmallestUnitTest {
@Nested
class Exceptions {
@Test
public void when_at_least_one_list_is_null_then_an_exception_is_thrown() {
Executable executable1 = () -> findKthSmallestElement(1, null, null);
Executable executable2 = () -> findKthSmallestElement(1, new int[]{2}, null);
Executable executable3 = () -> findKthSmallestElement(1, null, new int[]{2});
assertThrows(IllegalArgumentException.class, executable1);
assertThrows(IllegalArgumentException.class, executable2);
assertThrows(IllegalArgumentException.class, executable3);
}
@Test
public void when_at_least_one_list_is_empty_then_an_exception_is_thrown() {
Executable executable1 = () -> findKthSmallestElement(1, new int[]{}, new int[]{2});
Executable executable2 = () -> findKthSmallestElement(1, new int[]{2}, new int[]{});
Executable executable3 = () -> findKthSmallestElement(1, new int[]{}, new int[]{});
assertThrows(IllegalArgumentException.class, executable1);
assertThrows(IllegalArgumentException.class, executable2);
assertThrows(IllegalArgumentException.class, executable3);
}
@Test
public void when_k_is_smaller_than_0_then_an_exception_is_thrown() {
Executable executable1 = () -> findKthSmallestElement(-1, new int[]{2}, new int[]{2});
assertThrows(IllegalArgumentException.class, executable1);
}
@Test
public void when_k_is_smaller_than_1_then_an_exception_is_thrown() {
Executable executable1 = () -> findKthSmallestElement(0, new int[]{2}, new int[]{2});
assertThrows(IllegalArgumentException.class, executable1);
}
@Test
public void when_k_bigger_then_the_two_lists_then_an_exception_is_thrown() {
Executable executable1 = () -> findKthSmallestElement(6, new int[]{1, 5, 6}, new int[]{2, 5});
assertThrows(NoSuchElementException.class, executable1);
}
}
@Nested
class K_is_smaller_than_the_size_of_list1_and_the_size_of_list2 {
@Test
public void when_k_is_1_then_the_smallest_element_is_returned_from_list1() {
int result = findKthSmallestElement(1, new int[]{2, 7}, new int[]{3, 5});
assertEquals(2, result);
}
@Test
public void when_k_is_1_then_the_smallest_element_is_returned_list2() {
int result = findKthSmallestElement(1, new int[]{3, 5}, new int[]{2, 7});
assertEquals(2, result);
}
@Test
public void when_kth_element_is_smallest_element_and_occurs_in_both_lists() {
int[] list1 = new int[]{1, 2, 3};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(1, list1, list2);
assertEquals(1, result);
}
@Test
public void when_kth_element_is_smallest_element_and_occurs_in_both_lists2() {
int[] list1 = new int[]{1, 2, 3};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(2, list1, list2);
assertEquals(1, result);
}
@Test
public void when_kth_element_is_largest_element_and_occurs_in_both_lists_1() {
int[] list1 = new int[]{1, 2, 3};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(5, list1, list2);
assertEquals(3, result);
}
@Test
public void when_kth_element_is_largest_element_and_occurs_in_both_lists_2() {
int[] list1 = new int[]{1, 2, 3};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(6, list1, list2);
assertEquals(3, result);
}
@Test
public void when_kth_element_and_occurs_in_both_lists() {
int[] list1 = new int[]{1, 2, 3};
int[] list2 = new int[]{0, 2, 3};
int result = findKthSmallestElement(3, list1, list2);
assertEquals(2, result);
}
@Test
public void and_kth_element_is_in_first_list() {
int[] list1 = new int[]{1,2,3,4};
int[] list2 = new int[]{1,3,4,5};
int result = findKthSmallestElement(3, list1, list2);
assertEquals(2, result);
}
@Test
public void and_kth_is_in_second_list() {
int[] list1 = new int[]{1,3,4,4};
int[] list2 = new int[]{1,2,4,5};
int result = findKthSmallestElement(3, list1, list2);
assertEquals(2, result);
}
@Test
public void and_elements_in_first_list_are_all_smaller_than_second_list() {
int[] list1 = new int[]{1,3,7,9};
int[] list2 = new int[]{11,12,14,15};
int result = findKthSmallestElement(3, list1, list2);
assertEquals(7, result);
}
@Test
public void and_elements_in_first_list_are_all_smaller_than_second_list2() {
int[] list1 = new int[]{1,3,7,9};
int[] list2 = new int[]{11,12,14,15};
int result = findKthSmallestElement(4, list1, list2);
assertEquals(9, result);
}
@Test
public void and_only_elements_from_second_list_are_part_of_result() {
int[] list1 = new int[]{11,12,14,15};
int[] list2 = new int[]{1,3,7,9};
int result = findKthSmallestElement(3, list1, list2);
assertEquals(7, result);
}
@Test
public void and_only_elements_from_second_list_are_part_of_result2() {
int[] list1 = new int[]{11,12,14,15};
int[] list2 = new int[]{1,3,7,9};
int result = findKthSmallestElement(4, list1, list2);
assertEquals(9, result);
}
}
@Nested
class K_is_bigger_than_the_size_of_at_least_one_of_the_lists {
@Test
public void k_is_smaller_than_list1_and_bigger_than_list2() {
int[] list1 = new int[]{1, 2, 3, 4, 7, 9};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(5, list1, list2);
assertEquals(3, result);
}
@Test
public void k_is_bigger_than_list1_and_smaller_than_list2() {
int[] list1 = new int[]{1, 2, 3};
int[] list2 = new int[]{1, 2, 3, 4, 7, 9};
int result = findKthSmallestElement(5, list1, list2);
assertEquals(3, result);
}
@Test
public void when_k_is_bigger_than_the_size_of_both_lists_and_elements_in_second_list_are_all_smaller_than_first_list() {
int[] list1 = new int[]{9, 11, 13, 55};
int[] list2 = new int[]{1, 2, 3, 7};
int result = findKthSmallestElement(6, list1, list2);
assertEquals(11, result);
}
@Test
public void when_k_is_bigger_than_the_size_of_both_lists_and_elements_in_second_list_are_all_bigger_than_first_list() {
int[] list1 = new int[]{1, 2, 3, 7};
int[] list2 = new int[]{9, 11, 13, 55};
int result = findKthSmallestElement(6, list1, list2);
assertEquals(11, result);
}
@Test
public void when_k_is_bigger_than_the_size_of_both_lists() {
int[] list1 = new int[]{3, 7, 9, 11, 55};
int[] list2 = new int[]{1, 2, 3, 7, 13};
int result = findKthSmallestElement(7, list1, list2);
assertEquals(9, result);
}
@Test
public void when_k_is_bigger_than_the_size_of_both_lists_and_list1_has_more_elements_than_list2() {
int[] list1 = new int[]{3, 7, 9, 11, 55, 77, 100, 200};
int[] list2 = new int[]{1, 2, 3, 7, 13};
int result = findKthSmallestElement(11, list1, list2);
assertEquals(77, result);
}
@Test
public void max_test() {
int[] list1 = new int[]{100, 200};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(4, list1, list2);
assertEquals(100, result);
}
@Test
public void max_test2() {
int[] list1 = new int[]{100, 200};
int[] list2 = new int[]{1, 2, 3};
int result = findKthSmallestElement(5, list1, list2);
assertEquals(200, result);
}
@Test
public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_in_list2() {
int[] list1 = new int[]{1, 2, 5};
int[] list2 = new int[]{1, 3, 4, 7};
int result = findKthSmallestElement(4, list1, list2);
assertEquals(3, result);
}
@Test
public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_is_smallest_in_list2() {
int[] list1 = new int[]{1, 2, 5};
int[] list2 = new int[]{3, 4, 7};
int result = findKthSmallestElement(3, list1, list2);
assertEquals(3, result);
}
@Test
public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_is_smallest_in_list23() {
int[] list1 = new int[]{3, 11, 27, 53, 90};
int[] list2 = new int[]{4, 20, 21, 100};
int result = findKthSmallestElement(5, list1, list2);
assertEquals(21, result);
}
}
// @Test
// public void randomTests() {
// IntStream.range(1, 100000).forEach(i -> random());
// }
private void random() {
Random random = new Random();
int length1 = (Math.abs(random.nextInt())) % 1000 + 1;
int length2 = (Math.abs(random.nextInt())) % 1000 + 1;
int[] list1 = sortedRandomIntArrayOfLength(length1);
int[] list2 = sortedRandomIntArrayOfLength(length2);
int k = (Math.abs(random.nextInt()) % (length1 + length2)) + 1 ;
int result = findKthSmallestElement(k, list1, list2);
int result2 = getKthElementSorted(list1, list2, k);
int result3 = getKthElementMerge(list1, list2, k);
assertEquals(result2, result);
assertEquals(result2, result3);
}
private int[] sortedRandomIntArrayOfLength(int length) {
int[] intArray = new Random().ints(length).toArray();
Arrays.sort(intArray);
return intArray;
}
}