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BAEL-1297 Find kth largest element in a sequence of numbers (#3332) 

* Example Code For Evaluation Article

This is an example code for the evaluation article on "Different Types of Bean Injection in Spring"

* Added unit tests

* Minor changes to application context

* Removed code committed for evaluation article

* BAEL-944 Demonstrating the problems with new Url pattern matching in Spring 5

* BAEL-944 Demonstrating the problems with new Url pattern matching in Spring 5

* BAEL-944 Exploring the Spring MVC URL Matching Improvements

* BAEL-944 Exploring the Spring MVC URL Matching Improvements

* BAEL-944 Exploring the Spring MVC URL Matching Improvements

* BAEL-944 Code Formatting and solving build issue

* BAEL-944 Resolving build issue due to change in Spring version

* BAEL-944 Resolving build issue

* BAEL-944 Formatting code

* BAEL-944 Moving tests to correct package

* BAEL-944 Moving tests to correct package

* BAEL-944 Replacing @RequestMapping by @GetMapping

* BAEL-944 Remove unnecessary attribute name, "value" in annotations

* BAEL-79 Intro to Activiti with Spring

* BAEL-79 Intro to Activiti with Spring

* BAEL-79 Adding activiti module to the parent modules

* BAEL-79 Using latest version

* BAEL-79 Update Spring boot version that works with Activiti

* BAEL-79 Replace RequestMapping with GetMapping

* BAEL-79 Use Java 8 Syntax

* BAEL-79 Formatting

* BAEL-79 changed module name

* BAEL-378 A Guide to Activiti with Java

* BAEL-79 Fixed unit tests

* BAEL-79 Simplified the process

* BAEL-79 Fix test cases

* BAEL-1045 Lambda Behave

* BAEL-1045 Lambda Behave

* BAEL-1045 Lambda Behave

* BAEL-1090 Difference between compact and compressed strings in Java 9

* BAEL-1237 String Formatter

* BAEL-1237 String Formatter

* BAEL-1237 String Formatter

* BAEL-1237 String Formatter

* BAEL-1237 Guide to java.util.Formatter

* BAEL-1297 Find kth largest element in a sequence of numbers

* BAEL-1297 fixed issues and modified file name

* BAEL-1297 Modified randomized quickselect

* BAEL-1297 added additional sorting method

* BAEL-1297 UnitTest fix

* BAEL-1297 Additional method

Added QuickSelect With Iterative Partition method

* BAEL-1297 Added AssertJ annotations

* BAEL-1297 added missing assertj dependancy
This commit is contained in:
Mansi 2018-01-06 08:08:02 +05:30 committed by KevinGilmore
parent fe0e0ba115
commit 21c41cfd99
3 changed files with 174 additions and 0 deletions
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6
algorithms/pom.xml
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@ -39,6 +39,12 @@
<artifactId>jgrapht-core</artifactId>
<version>1.0.1</version>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>3.9.0</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>

111
algorithms/src/main/java/com/baeldung/algorithms/kthlargest/FindKthLargest.java Normal file
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@ -0,0 +1,111 @@
package com.baeldung.algorithms.kthlargest;
import java.util.Arrays;
import java.util.Collections;
import java.util.stream.IntStream;
public class FindKthLargest {
public int findKthLargestBySorting(Integer[] arr, int k) {
Arrays.sort(arr);
int targetIndex = arr.length - k;
return arr[targetIndex];
}
public int findKthLargestBySortingDesc(Integer[] arr, int k) {
Arrays.sort(arr, Collections.reverseOrder());
return arr[k - 1];
}
public int findKthElementByQuickSelect(Integer[] arr, int left, int right, int k) {
if (k >= 0 && k <= right - left + 1) {
int pos = partition(arr, left, right);
if (pos - left == k) {
return arr[pos];
}
if (pos - left > k) {
return findKthElementByQuickSelect(arr, left, pos - 1, k);
}
return findKthElementByQuickSelect(arr, pos + 1, right, k - pos + left - 1);
}
return 0;
}
public int findKthElementByQuickSelectWithIterativePartition(Integer[] arr, int left, int right, int k) {
if (k >= 0 && k <= right - left + 1) {
int pos = partitionIterative(arr, left, right);
if (pos - left == k) {
return arr[pos];
}
if (pos - left > k) {
return findKthElementByQuickSelectWithIterativePartition(arr, left, pos - 1, k);
}
return findKthElementByQuickSelectWithIterativePartition(arr, pos + 1, right, k - pos + left - 1);
}
return 0;
}
private int partition(Integer[] arr, int left, int right) {
int pivot = arr[right];
Integer[] leftArr;
Integer[] rightArr;
leftArr = IntStream.range(left, right)
.filter(i -> arr[i] < pivot)
.map(i -> arr[i])
.boxed()
.toArray(Integer[]::new);
rightArr = IntStream.range(left, right)
.filter(i -> arr[i] > pivot)
.map(i -> arr[i])
.boxed()
.toArray(Integer[]::new);
int leftArraySize = leftArr.length;
System.arraycopy(leftArr, 0, arr, left, leftArraySize);
arr[leftArraySize + left] = pivot;
System.arraycopy(rightArr, 0, arr, left + leftArraySize + 1, rightArr.length);
return left + leftArraySize;
}
private int partitionIterative(Integer[] arr, int left, int right) {
int pivot = arr[right], i = left;
for (int j = left; j <= right - 1; j++) {
if (arr[j] <= pivot) {
swap(arr, i, j);
i++;
}
}
swap(arr, i, right);
return i;
}
public int findKthElementByRandomizedQuickSelect(Integer[] arr, int left, int right, int k) {
if (k >= 0 && k <= right - left + 1) {
int pos = randomPartition(arr, left, right);
if (pos - left == k) {
return arr[pos];
}
if (pos - left > k) {
return findKthElementByRandomizedQuickSelect(arr, left, pos - 1, k);
}
return findKthElementByRandomizedQuickSelect(arr, pos + 1, right, k - pos + left - 1);
}
return 0;
}
private int randomPartition(Integer arr[], int left, int right) {
int n = right - left + 1;
int pivot = (int) (Math.random()) % n;
swap(arr, left + pivot, right);
return partition(arr, left, right);
}
private void swap(Integer[] arr, int n1, int n2) {
int temp = arr[n2];
arr[n2] = arr[n1];
arr[n1] = temp;
}
}

57
algorithms/src/test/java/com/baeldung/algorithms/kthlargest/FindKthLargestUnitTest.java Normal file
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@ -0,0 +1,57 @@
package com.baeldung.algorithms.kthlargest;
import static org.assertj.core.api.Assertions.*;
import org.junit.Before;
import org.junit.Test;
public class FindKthLargestUnitTest {
private FindKthLargest findKthLargest;
private Integer[] arr = { 3, 7, 1, 2, 8, 10, 4, 5, 6, 9 };
@Before
public void setup() {
findKthLargest = new FindKthLargest();
}
@Test
public void givenIntArray_whenFindKthLargestBySorting_thenGetResult() {
int k = 3;
assertThat(findKthLargest.findKthLargestBySorting(arr, k)).isEqualTo(8);
}
@Test
public void givenIntArray_whenFindKthLargestBySortingDesc_thenGetResult() {
int k = 3;
assertThat(findKthLargest.findKthLargestBySortingDesc(arr, k)).isEqualTo(8);
}
@Test
public void givenIntArray_whenFindKthLargestByQuickSelect_thenGetResult() {
int k = 3;
int kthLargest = arr.length - k;
assertThat(findKthLargest.findKthElementByQuickSelect(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
}
@Test
public void givenIntArray_whenFindKthElementByQuickSelectIterative_thenGetResult() {
int k = 3;
int kthLargest = arr.length - k;
assertThat(findKthLargest.findKthElementByQuickSelectWithIterativePartition(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
}
@Test
public void givenIntArray_whenFindKthSmallestByQuickSelect_thenGetResult() {
int k = 3;
assertThat(findKthLargest.findKthElementByQuickSelect(arr, 0, arr.length - 1, k - 1)).isEqualTo(3);
}
@Test
public void givenIntArray_whenFindKthLargestByRandomizedQuickSelect_thenGetResult() {
int k = 3;
int kthLargest = arr.length - k;
assertThat(findKthLargest.findKthElementByRandomizedQuickSelect(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
}
}