diff --git a/src/main/java/com/williamfiset/algorithms/graphtheory/HamiltonianCycle.java b/src/main/java/com/williamfiset/algorithms/graphtheory/HamiltonianCycle.java
new file mode 100644
index 000000000..9cbf8b8aa
--- /dev/null
+++ b/src/main/java/com/williamfiset/algorithms/graphtheory/HamiltonianCycle.java
@@ -0,0 +1,99 @@
+package com.williamfiset.algorithms.graphtheory;
+
+import java.util.List;
+import java.util.Scanner;
+import java.util.Arrays;
+
+public class HamiltonianCycle {
+    private int[]   path;
+    private int[][] graph;
+    private boolean flag=false;
+    public void setGraph(int[][] graph1){
+        this.graph=graph1;
+    }
+
+    public int[] getPath(){
+        return this.path;
+    }
+
+    public void getHamiltonCircuit(int[][] g) {
+        if(g==null)throw new IllegalArgumentException("Graph cannot be null.");
+        //used to record the circuit
+        boolean[] used = new boolean[g.length];
+        int[] path = new int[g.length];
+        for(int i = 0;i < g.length;i++) {
+            //initialise
+            used[i] = false;
+            path[i] = -1;
+        }
+        used[0] = true;
+        //the start point
+        path[0] = 0;
+        //deep search from the first point
+        dfs(g, path, used, 1);
+        if(!flag){
+            System.out.print("No solution");
+        }
+    }
+    /*
+     * step means the current walked points' number
+     */
+    public boolean dfs(int[][] g, int[] path, boolean[] used, int step) {
+        if(step == g.length) {     //when finish all points
+            if(g[path[step - 1]][0] == 1) {
+                storeResult(path);
+                flag=true;
+                //the last step can reach the end
+                for(int i = 0;i < path.length;i++)
+                    System.out.print(path[i]+">");
+                System.out.print(path[0]);
+                System.out.println();
+                return true;
+            }
+            return false;
+        } else {
+            storeResult(path);
+            for(int i = 0;i < g.length;i++) {
+                if(!used[i] && g[path[step - 1]][i] == 1) {
+                    used[i] = true;
+                    path[step] = i;
+                    if(dfs(g, path, used, step + 1))
+                        return true;
+                    else {
+                        used[i] = false;
+                        path[step] = -1;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+
+    public void storeResult(int [] path){
+        this.path=new int[path.length+1];
+        for(int i=0;i< path.length;i++){
+            this.path[i]=path[i];
+        }
+        this.path[path.length]=path[0];
+    }
+
+    public static void main(String[] args) {
+        HamiltonianCycle hc = new HamiltonianCycle();
+        Scanner scan = new Scanner(System.in);
+            // Make an object of HamiltonianCycle class
+            // Accept number of vertices
+        System.out.println("Enter number of vertices");
+        int n = scan.nextInt();
+            // get graph
+        System.out.println("Enter adjacency matrix");
+        int[][] graph = new int[n][n];
+        for (int i = 0; i < n; i++)
+            for (int j = 0; j < n; j++)
+                graph[i][j] = scan.nextInt();
+        hc.getHamiltonCircuit(graph);
+        scan.close();
+    }
+
+
+}
+
diff --git a/src/main/java/com/williamfiset/algorithms/sorting/CombSort.java b/src/main/java/com/williamfiset/algorithms/sorting/CombSort.java
new file mode 100644
index 000000000..f9eaac839
--- /dev/null
+++ b/src/main/java/com/williamfiset/algorithms/sorting/CombSort.java
@@ -0,0 +1,73 @@
+package com.williamfiset.algorithms.sorting;
+
+import java.util.Scanner;
+
+class CombSort
+{
+    // To find gap between elements
+    int getNextGap(int gap)
+    {
+        // Shrink gap by Shrink factor
+        gap = (gap*10)/13;
+        if (gap < 1)
+            return 1;
+        return gap;
+    }
+
+    // Function to sort arr[] using Comb Sort
+    void sort(int arr[])
+    {
+        int n = arr.length;
+
+        // initialize gap
+        int gap = n;
+
+        // Initialize swapped as true to make sure that
+        // loop runs
+        boolean swapped = true;
+
+        // Keep running while gap is more than 1 and last
+        // iteration caused a swap
+        while (gap != 1 || swapped == true)
+        {
+            // Find next gap
+            gap = getNextGap(gap);
+            // Initialize swapped as false so that we can
+            // check if swap happened or not
+            swapped = false;
+
+            // Compare all elements with current gap
+            for (int i=0; i<n-gap; i++)
+            {
+                if (arr[i] > arr[i+gap])
+                {
+                    // Swap arr[i] and arr[i+gap]
+                    int temp = arr[i];
+                    arr[i] = arr[i+gap];
+                    arr[i+gap] = temp;
+
+                    // Set swapped
+                    swapped = true;
+                }
+            }
+        }
+    }
+
+    // Driver method
+    public static void main(String args[])
+    {
+        CombSort ob = new CombSort();
+        Scanner scan = new Scanner(System.in);
+        System.out.println("Enter number of the numbers you want to sort");
+        int V = scan.nextInt();
+        System.out.println("Enter the numbers:");
+        int[] arr = new int[V];
+        for (int i=0;i<V;i++)
+            arr[i]=scan.nextInt();
+        ob.sort(arr);
+        System.out.println("sorted array");
+        for (int i=0; i<arr.length; ++i)
+            System.out.print(arr[i] + " ");
+
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/com/williamfiset/algorithms/graphtheory/HamiltonianCycleTest.java b/src/test/java/com/williamfiset/algorithms/graphtheory/HamiltonianCycleTest.java
new file mode 100644
index 000000000..be07fa4a1
--- /dev/null
+++ b/src/test/java/com/williamfiset/algorithms/graphtheory/HamiltonianCycleTest.java
@@ -0,0 +1,124 @@
+package com.williamfiset.algorithms.graphtheory;
+
+import org.junit.*;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.*;
+
+import static com.google.common.truth.Truth.assertThat;
+
+public class HamiltonianCycleTest {
+
+   HamiltonianCycle solver;
+
+    @Before
+    public void setUp() {
+        solver = null;
+    }
+
+    // Initialize graph with 'n' nodes.
+    public static int[][] initializeEmptyGraph() {
+        int[][] graph = null;
+        return graph;
+    }
+
+    // Add directed edge to graph.
+    public static void addDirectedEdge(int[][] graph, int a, int b) {
+        graph[a][b]=1;
+    }
+
+    //test empty
+    @Test(expected = IllegalArgumentException.class)
+    public void testEmptyGraph() {
+        int[][] graph = initializeEmptyGraph();
+        HamiltonianCycle solver;
+        solver = new HamiltonianCycle();
+        solver.setGraph(graph);
+        solver.getHamiltonCircuit(graph);
+    }
+
+    //valid test 1
+    @Test
+    public void validHC1() {
+        int[][] graph = new int[5][5];
+        int[] result= new int[6];
+        result[0]=0;result[1]=1;result[2]=2;result[3]=4;result[4]=3;result[5]=0;
+        /**
+         * the example graph
+         * (0)--(1)--(2)
+         *  |   / \   |
+         *  |  /   \  |
+         *  | /     \ |
+         * (3)-------(4)
+         *
+         * the 2D should be
+         * 0 1 0 1 0
+         * 1 0 1 1 1
+         * 0 1 0 0 1
+         * 1 1 0 0 1
+         * 0 1 1 1 0
+         *
+         */
+        graph [0][0]=0;graph [0][1]=1;graph [0][2]=0;graph [0][3]=1;graph [0][4]=0;
+        graph [1][0]=1;graph [1][1]=0;graph [1][2]=1;graph [1][3]=1;graph [1][4]=1;
+        graph [2][0]=0;graph [2][1]=1;graph [2][2]=0;graph [2][3]=0;graph [2][4]=1;
+        graph [3][0]=1;graph [3][1]=1;graph [3][2]=0;graph [3][3]=0;graph [3][4]=1;
+        graph [4][0]=0;graph [4][1]=1;graph [4][2]=1;graph [4][3]=1;graph [4][4]=0;
+        HamiltonianCycle solver;
+        solver = new HamiltonianCycle();
+        solver.setGraph(graph);
+        solver.getHamiltonCircuit(graph);
+        assertThat(solver.getPath()).isEqualTo(result);
+    }
+
+    //invalid test 1, generally same as valid 1, but change a little and make it invalid
+    private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
+    private final ByteArrayOutputStream errContent = new ByteArrayOutputStream();
+    private final PrintStream originalOut = System.out;
+    private final PrintStream originalErr = System.err;
+
+    @Before
+    public void setUpStreams() {
+        System.setOut(new PrintStream(outContent));
+        System.setErr(new PrintStream(errContent));
+    }
+
+    @After
+    public void restoreStreams() {
+        System.setOut(originalOut);
+        System.setErr(originalErr);
+    }
+    @Test
+    public void invalidHC1() {
+        int[][] graph = new int[5][5];
+        int[] invalidresult= new int[6];
+        Arrays.fill(invalidresult, -1);
+        /**
+         * the example graph
+         * (0)--(1)--(2)
+         *  |   / \   |
+         *  |  /   \  |
+         *  | /     \ |
+         * (3)      (4)
+         *
+         * the 2D should be
+         * 0 1 0 1 0
+         * 1 0 1 1 1
+         * 0 1 0 0 1
+         * 1 1 0 0 0
+         * 0 1 1 0 0
+         *
+         */
+        graph [0][0]=0;graph [0][1]=1;graph [0][2]=0;graph [0][3]=1;graph [0][4]=0;
+        graph [1][0]=1;graph [1][1]=0;graph [1][2]=1;graph [1][3]=1;graph [1][4]=1;
+        graph [2][0]=0;graph [2][1]=1;graph [2][2]=0;graph [2][3]=0;graph [2][4]=1;
+        graph [3][0]=1;graph [3][1]=1;graph [3][2]=0;graph [3][3]=0;graph [3][4]=0;
+        graph [4][0]=0;graph [4][1]=1;graph [4][2]=1;graph [4][3]=0;graph [4][4]=0;
+        HamiltonianCycle solver;
+        solver = new HamiltonianCycle();
+        solver.setGraph(graph);
+        solver.getHamiltonCircuit(graph);
+        Assert.assertEquals("No solution",outContent.toString());
+    }
+}
diff --git a/src/test/java/com/williamfiset/algorithms/sorting/CombSortTest.java b/src/test/java/com/williamfiset/algorithms/sorting/CombSortTest.java
new file mode 100644
index 000000000..164499c82
--- /dev/null
+++ b/src/test/java/com/williamfiset/algorithms/sorting/CombSortTest.java
@@ -0,0 +1,49 @@
+package com.williamfiset.algorithms.sorting;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Random;
+
+import static com.google.common.truth.Truth.assertThat;
+
+public class CombSortTest {
+    static Random random = new Random();
+
+    CombSort ob = new CombSort();
+
+    @Test
+    public void randomCombSort_smallNumbers() {
+        for (int size = 0; size < 1000; size++) {
+            int[] values = new int[size];
+            for (int i = 0; i < size; i++) {
+                values[i] = randInt(1, 50);
+            }
+            int[] copy = values.clone();
+
+            Arrays.sort(values);
+            ob.sort(copy);            assertThat(values).isEqualTo(copy);
+        }
+    }
+
+    @Test
+    public void randomRadixSort_largeNumbers() {
+        for (int size = 0; size < 1000; size++) {
+            int[] values = new int[size];
+            for (int i = 0; i < size; i++) {
+                values[i] = randInt(1, Integer.MAX_VALUE);
+            }
+            int[] copy = values.clone();
+
+            Arrays.sort(values);
+            ob.sort(copy);
+
+            assertThat(values).isEqualTo(copy);
+        }
+    }
+
+    // return a random number between [min, max]
+    static int randInt(int min, int max) {
+        return random.nextInt((max - min) + 1) + min;
+    }
+}