Added Insertion sort

src/TechInterview/InsertionSort.java

@@ -0,0 +1,59 @@
+package TechInterview;
+
+import java.util.Arrays;
+import static java.lang.System.out;
+
+/**
+ * @author gavin
+ */
+public class InsertionSort {
+
+    /**
+     * Sorts the parameter in-place
+     *
+     * @param list an array
+     */
+    public static final void sort(int[] list) {
+        if (null == list || list.length <= 1) {
+            return;
+        }
+
+        for (int i = 1; i < list.length; i++) {
+            int j = i;
+            while (j > 0 && (list[j - 1] > list[j])) {
+                swap(list, j);
+                j--;
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        int[] nullList = null;
+        int[] emptyList = new int[0];
+        int[] singleItemList = {23};
+        int[] nonEmptyList = {23, 44, 1, 209, 2, 88, 13, 37};
+        int[] worstcaseList = {209, 88, 44, 37, 23, 13, 2, 1};
+        int[] sortedList = {1, 2, 13, 23, 37, 44, 88, 209};
+
+        insertionSort(nullList, "null list");
+        insertionSort(emptyList, "empty list");
+        insertionSort(singleItemList, "single item list");
+        insertionSort(nonEmptyList, "non empty list");
+        insertionSort(worstcaseList, "worse case list");
+        insertionSort(sortedList, "already sorted list");
+    }
+
+    private static void insertionSort(int[] list, String comment) {
+        out.println(comment);
+        out.println("\tbefore: " + Arrays.toString(list));
+        sort(list);
+        out.println("\t after: " + Arrays.toString(list));
+    }
+
+    private static void swap(int[] list, int j) {
+        int prev = list[j - 1];
+        int next = list[j];
+        list[j - 1] = next;
+        list[j] = prev;
+    }
+}