RandomProblem002.java matrix multiplication

java8/src/main/java/com/shekhargulati/ninetynine_problems/java8/_00_random/RandomProblem02.java → java8/src/main/java/com/shekhargulati/ninetynine_problems/java8/_00_random/RandomProblem002.java

@@ -3,7 +3,7 @@
 /**
  * Given a text and a string pattern check if pattern exist in the text.
  */
-public class RandomProblem02 {
+public class RandomProblem002 {
 
     public static boolean patternExistInText(String text, String pattern) {
         /*

java8/src/main/java/com/shekhargulati/ninetynine_problems/java8/_00_random/RandomProblem003.java

@@ -0,0 +1,37 @@
+package com.shekhargulati.ninetynine_problems.java8._00_random;
+
+/**
+ * Perform matrix multiplication of two arrays.
+ * Matrix multiplication of array A of size nxm and array B of size mxp is an array of size nxp
+ */
+public class RandomProblem003 {
+
+    public static int[][] matrixMultiplication(int[][] a, int[][] b) {
+        /*
+        1. Iterate over all the rows of A
+        2. For each row of A
+            2.1 iterate over all the columns of A and multiply them with each column of B
+         */
+        int rowsA = a.length;
+        int colsA = a[0].length;
+        int rowsB = b.length;
+        int colsB = b[0].length;
+
+
+        if (colsA != rowsB) {
+            throw new IllegalArgumentException("Can't perform matrix calculation on matrix with given sizes");
+        }
+        int[][] result = new int[rowsA][colsB];
+
+        for (int i = 0; i < rowsA; i++) {
+            for (int j = 0; j < colsB; j++) {
+                int fValue = 0;
+                for (int k = 0; k < colsA; k++) {
+                    fValue += a[i][k] * b[k][j];
+                }
+                result[i][j] = fValue;
+            }
+        }
+        return result;
+    }
+}

java8/src/test/java/com/shekhargulati/ninetynine_problems/java8/_00_random/RandomProblem02Test.java → java8/src/test/java/com/shekhargulati/ninetynine_problems/java8/_00_random/RandomProblem002Test.java

@@ -9,19 +9,19 @@
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
-public class RandomProblem02Test {
+public class RandomProblem002Test {
 
     @Test
     public void shouldGiveTrueWhenPatternExistInText() throws Exception {
         String text = Files.lines(Paths.get("src", "test", "resources", "book.txt")).collect(joining());
-        boolean patternExists = RandomProblem02.patternExistInText(text, "prudent");
+        boolean patternExists = RandomProblem002.patternExistInText(text, "prudent");
         assertTrue(patternExists);
     }
 
     @Test
     public void shouldGiveFalseWhenPatternDoesNotExistInText() throws Exception {
         String text = Files.lines(Paths.get("src", "test", "resources", "book.txt")).collect(joining());
-        boolean patternExists = RandomProblem02.patternExistInText(text, "awesome");
+        boolean patternExists = RandomProblem002.patternExistInText(text, "awesome");
         assertFalse(patternExists);
     }
 }

java8/src/test/java/com/shekhargulati/ninetynine_problems/java8/_00_random/RandomProblem003Test.java

@@ -0,0 +1,31 @@
+package com.shekhargulati.ninetynine_problems.java8._00_random;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+public class RandomProblem003Test {
+
+    @Test
+    public void performMatrixMultiplicationOfTwoArrays() throws Exception {
+        int[][] a = {
+                {1, 2, 3},
+                {4, 5, 6}
+        };
+
+        int[][] b = {
+                {7, 8},
+                {9, 10},
+                {11, 12}
+        };
+
+        int[][] result = {
+                {58, 64},
+                {139, 154}
+        };
+
+        int[][] c = RandomProblem003.matrixMultiplication(a, b);
+        assertThat(c, equalTo(result));
+    }
+}