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Commit ff3a90d

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add SelectionProblem
1 parent 0eb17a2 commit ff3a90d

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4 files changed

+91
-76
lines changed

4 files changed

+91
-76
lines changed

‎src/main/java/ir/sk/algorithm/mathematic/Mathematical.java‎

Lines changed: 0 additions & 61 deletions
Original file line numberDiff line numberDiff line change
@@ -500,67 +500,6 @@ public static double meanUsingCountingSort(int array[]) {
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return mode;
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}
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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/**
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* median = "the middle" value
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*/
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@TimeComplexity("O(n Log n) as we need to sort the array first")
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public static double median(int a[]) {
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// First we sort the array
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Arrays.sort(a);
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// check for even case
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if (a.length % 2 != 0)
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return a[a.length / 2];
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return (double) (a[(a.length - 1) / 2] + a[a.length / 2]) / 2.0;
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}
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@TimeComplexity("O(n + p) = O(n)")
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@SpaceComplexity("O(p) where P is the size of auxiliary array")
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public static double medianUsingCountingSort(int[] array) {
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int n = array.length;
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int max = Arrays.stream(array).max().getAsInt();
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// Frequency Array
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int[] counting = new int[max + 1];
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// store count of each character
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for (int i = 0; i < n; i++) {
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counting[array[i]]++;
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}
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double median = 0;
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if (n % 2 == 0) {
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Integer m1 = null;
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Integer m2 = null;
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int count = 0;
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for (int j = 0; j < counting.length; j++) {
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count += counting[j];
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if (m1 == null && count >= n / 2) {
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m1 = j;
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}
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if (m2 == null && count >= n / 2 + 1) {
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m2 = j;
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break;
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}
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}
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median = (m1 + m2) / 2.0;
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} else {
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int count = 0;
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for (int j = 0; j < counting.length; j++) {
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count += counting[j];
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if (count > n / 2) {
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median = j;
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break;
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}
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}
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}
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return median;
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}
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/**
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* Mode = frequently occurring element in an array
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*/
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,69 @@
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package ir.sk.algorithm.mathematic;
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import java.util.*;
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import ir.sk.helper.complexity.SpaceComplexity;
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import ir.sk.helper.complexity.TimeComplexity;
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public class SelectionProblem {
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/**
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* median = "the middle" value
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*/
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@TimeComplexity("O(n Log n) as we need to sort the array first")
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public static double median(int a[]) {
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// First we sort the array
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Arrays.sort(a);
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// check for even case
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if (a.length % 2 != 0)
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return a[a.length / 2];
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return (double) (a[(a.length - 1) / 2] + a[a.length / 2]) / 2.0;
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}
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@TimeComplexity("O(n + p) = O(n)")
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@SpaceComplexity("O(p) where P is the size of auxiliary array")
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public static double medianUsingCountingSort(int[] array) {
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int n = array.length;
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int max = Arrays.stream(array).max().getAsInt();
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// Frequency Array
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int[] counting = new int[max + 1];
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// store count of each character
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for (int i = 0; i < n; i++) {
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counting[array[i]]++;
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}
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double median = 0;
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if (n % 2 == 0) {
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Integer m1 = null;
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Integer m2 = null;
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int count = 0;
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for (int j = 0; j < counting.length; j++) {
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count += counting[j];
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if (m1 == null && count >= n / 2) {
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m1 = j;
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}
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if (m2 == null && count >= n / 2 + 1) {
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m2 = j;
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break;
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}
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}
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median = (m1 + m2) / 2.0;
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} else {
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int count = 0;
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for (int j = 0; j < counting.length; j++) {
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count += counting[j];
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if (count > n / 2) {
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median = j;
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break;
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}
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}
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}
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return median;
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}
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}

‎src/test/java/ir/sk/algorithm/array/MathematicalTest.java‎

Lines changed: 0 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -124,21 +124,6 @@ public void meanUsingCountingSort() {
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Assert.assertEquals(expectedValue, Mathematical.meanUsingCountingSort(a) + "");
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}
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@Test
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public void median() {
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int a[] = {1, 3, 4, 2, 7, 5, 8, 6};
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String expectedValue = "4.5";
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Assert.assertEquals(expectedValue, Mathematical.median(a) + "");
133-
}
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@Test
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public void medianUsingCountingSort() {
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int a[] = {1, 3, 4, 2, 7, 5, 8, 6};
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String expectedValue = "4.5";
139-
Assert.assertEquals(expectedValue, Mathematical.medianUsingCountingSort(a) + "");
140-
}
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@Test
143128
public void isPrime() {
144129
boolean expectedValue = true;
Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,22 @@
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package ir.sk.algorithm.array;
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import org.junit.Assert;
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import org.junit.Test;
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import ir.sk.algorithm.mathematic.SelectionProblem;
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public class SelectionProblemTest {
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@Test
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public void median() {
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int a[] = {1, 3, 4, 2, 7, 5, 8, 6};
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String expectedValue = "4.5";
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Assert.assertEquals(expectedValue, SelectionProblem.median(a) + "");
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}
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@Test
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public void medianUsingCountingSort() {
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int a[] = {1, 3, 4, 2, 7, 5, 8, 6};
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String expectedValue = "4.5";
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Assert.assertEquals(expectedValue, SelectionProblem.medianUsingCountingSort(a) + "");
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}
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}

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