Add insertion sort algorithm

.idea/codeStyles/Project.xml

@@ -24,5 +24,29 @@
         <option name="ITERATION_ELEMENTS_WRAPPING" value="chop_down_if_not_single" />
       </formatting-settings>
     </DBN-SQL>
+    <DBN-PSQL>
+      <case-options enabled="false">
+        <option name="KEYWORD_CASE" value="lower" />
+        <option name="FUNCTION_CASE" value="lower" />
+        <option name="PARAMETER_CASE" value="lower" />
+        <option name="DATATYPE_CASE" value="lower" />
+        <option name="OBJECT_CASE" value="preserve" />
+      </case-options>
+      <formatting-settings enabled="false" />
+    </DBN-PSQL>
+    <DBN-SQL>
+      <case-options enabled="false">
+        <option name="KEYWORD_CASE" value="lower" />
+        <option name="FUNCTION_CASE" value="lower" />
+        <option name="PARAMETER_CASE" value="lower" />
+        <option name="DATATYPE_CASE" value="lower" />
+        <option name="OBJECT_CASE" value="preserve" />
+      </case-options>
+      <formatting-settings enabled="false">
+        <option name="STATEMENT_SPACING" value="one_line" />
+        <option name="CLAUSE_CHOP_DOWN" value="chop_down_if_statement_long" />
+        <option name="ITERATION_ELEMENTS_WRAPPING" value="chop_down_if_not_single" />
+      </formatting-settings>
+    </DBN-SQL>
   </code_scheme>
 </component>

README.md

@@ -3,12 +3,15 @@
 This repository is meant for me to compile a list of examples of different 
 algorithms that I have learned of, and develop a working implementation. 
 These implementations may not be the most efficient, so please do point it 
-out to me if you see something that could be improved upon.
+out to me if you see something that could be improved upon. The complexity 
+notations were taken from the  [Big O Cheatsheet](http://bigocheatsheet.com/)
 
-## Sorting
+### Sorting
 
-- [Merge Sort](sorting/src/main/java/com/wbrawner/algorithms/sorting/MergeSort.java)
-  - [Tests](sorting/src/test/java/com/wbrawner/algorithms/sorting/ParameterizedMergeSortTest.java) 
+Algorithm|Implementation|Tests|Worst Time Complexity|Worst Space Complexity
+-----|-----|-----|-----|-----
+[Insertion Sort](https://en.wikipedia.org/wiki/Insertion_sort)|[InsertionSort.java](sorting/src/main/java/com/wbrawner/algorithms/sorting/InsertionSort.java)|[ParameterizedInsertionSortTest.java](sorting/src/test/java/com/wbrawner/algorithms/sorting/ParameterizedInsertionSortTest.java)|O(n²)|O(1)
+[Merge Sort](https://en.wikipedia.org/wiki/Merge_sort)|[MergeSort.java](sorting/src/main/java/com/wbrawner/algorithms/sorting/MergeSort.java)|[ParameterizedMergeSortTest.java](sorting/src/test/java/com/wbrawner/algorithms/sorting/ParameterizedMergeSortTest.java)|O(n log(n))|O(n)
 
 ## Building/Testing
 
@@ -16,4 +19,4 @@ out to me if you see something that could be improved upon.
     
 To keep things simple, the tests share the same data where possible.
 
-- [Sorting test data](sorting/src/test/java/com/wbrawner/algorithms/sorting/SortData.java)
+- [Sorting algorithms test data](sorting/src/test/java/com/wbrawner/algorithms/sorting/SortData.java)

sorting/src/main/java/com/wbrawner/algorithms/sorting/InsertionSort.java

@@ -0,0 +1,33 @@
+package com.wbrawner.algorithms.sorting;
+
+/**
+ * The Insertion Sort algorithm modifies an array in place, removing the
+ * first untouched index and iterating over the already sorted indices
+ * to position the removed index correctly.
+ */
+public class InsertionSort {
+    /**
+     * Sort a given array of ints using the Insertion Sort algorithm
+     *
+     * @param array an unsorted array of ints
+     * @return a sorted array of ints
+     */
+    public static int[] sort(int[] array) {
+        // An empty array or array with only a single value can't be sorted
+        if (array.length < 2) {
+            return array;
+        }
+
+        for (int i = 1; i < array.length; i++) {
+            int currentValue = array[i];
+            int j = i - 1;
+            while (j >= 0 && array[j] > currentValue) {
+                array[j + 1] = array[j];
+                j--;
+            }
+            array[j + 1] = currentValue;
+        }
+
+        return array;
+    }
+}

sorting/src/test/java/com/wbrawner/algorithms/sorting/ParameterizedInsertionSortTest.java

@@ -0,0 +1,31 @@
+package com.wbrawner.algorithms.sorting;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import static org.junit.Assert.assertArrayEquals;
+
+@RunWith(Parameterized.class)
+public class ParameterizedInsertionSortTest {
+
+
+    @Parameterized.Parameter(1)
+    public int[] sorted;
+
+    @Parameterized.Parameter()
+    public int[] unsorted;
+
+    @Test
+    public void sortTest() {
+        assertArrayEquals(
+                sorted,
+                InsertionSort.sort(unsorted)
+        );
+    }
+
+    @Parameterized.Parameters
+    public static int[][][] getData() {
+        return SortData.get();
+    }
+}