Quick sort implementation

module5/src/main/java/com/hithomelabs/princeton1/module5/AbstractCustomSorts.java

@@ -6,6 +6,9 @@ public abstract class AbstractCustomSorts<E> {
 
     // TODO: Implement this method
     public void exch(E[] arr, int j, int i) {
+        E temp = arr[i];
+        arr[i] = arr[j];
+        arr[j] = temp;
     }
 
     // TODO: Implement this method

module7/src/main/java/com/hithomelabs/princeton1/module7/Quick.java

@@ -6,6 +6,51 @@ import com.hithomelabs.princeton1.module5.AbstractCustomSorts;
 public class Quick<E> extends AbstractCustomSorts<E> {
     @Override
     public void sort(E[] arr) {
+        randomShuffle(arr);
+        partition(arr, 0, arr.length-1);
+    }
 
+    private void randomShuffle(E[] arr){
+        int array_len = arr.length;
+        for(int i=0; i< array_len; i++){
+            int random_index = (int)(Math.random()*array_len);
+            exch(arr, i, random_index);
+        }
+    }
+
+    private void partition(E[] arr, int low, int high){
+        if(low >= high)
+            return;
+        int mid = sort(arr, low, high);
+        partition(arr, low, mid-1);
+        partition(arr, mid + 1, high);
+    }
+
+    private int sort(E[] arr, int low, int high){
+        int i = low+1;
+        int j = high;
+        while (true){
+            // Find the i index greater than 1st element
+            while (i<=high && !less((Comparable<E>) arr[low], arr[i]))
+                i++;
+            // Find the j index less than 1st element
+            while (!less((Comparable<E>) arr[j], arr[low]) && j > low)
+                j--;
+            // Break if indexes are crossed
+            if(j <= i)
+                break;
+            // Swap index values of i & j
+            if(less((Comparable<E>) arr[j], arr[i]))
+                exch(arr, i++, j--);
+        }
+        // Swap 1st element to it's correct position
+        int k_index = low+1;
+        while (k_index <= high){
+            if(less((Comparable<E>) arr[low], arr[k_index]))
+                break;
+            k_index++;
+        }
+        exch(arr, low, k_index-1);
+        return k_index - 1;
     }
 }