Added READMEs

Author: kaitinghh

assets/ParanoidQuickSort.jpeg

@@ -89,7 +89,7 @@ private static int partition(int[] arr, int start, int end) {
         int pIdx = random(start, end);
         int pivot = arr[pIdx];
 
-        swap(arr, start, pIdx);
+        swap(arr, start, pIdx); // swap the pivot to the start of the array
 
         int less = start + 1;
 
@@ -100,7 +100,7 @@ private static int partition(int[] arr, int start, int end) {
             }
         }
 
-        swap(arr, less - 1, start);
+        swap(arr, less - 1, start); // swap the pivot to its correct position
 
         return less - 1;
     }

assets/QuickSortFirstPivot.png

@@ -0,0 +1,11 @@
+This is how QuickSort works if we always pick the first element as the pivot. 
+
+![QuickSort with first element as pivot](../../../../../assets/QuickSortFirstPivot.png)
+
+Image Source: https://www.geeksforgeeks.org/implement-quicksort-with-first-element-as-pivot/
+
+If we use randomised pivot selection, the idea is very similar to the above implementation. All we 
+need to do is to swap the random pivot to the first element in the array, then partition as per usual, 
+then swap the pivot back to its correct position. Below is an illustration: 
+
+![Lomuto's QuickSort with random pivot](../../../../../assets/QuickSortRandomPivot.jpeg)

assets/QuickSortRandomPivot.jpeg

@@ -0,0 +1 @@
+![ParanoidQuickSort](../../../../../assets/ParanoidQuickSort.jpeg)

assets/ThreeWayPartitioning.jpeg

@@ -11,6 +11,10 @@
  * elements equal to the pivot, and elements greater than the pivot. By doing so, we can avoid unnecessary comparisons
  * and swaps with duplicate elements, making the sorting process more efficient.
  *
+ * Implementation Invariant:
+ * The pivot and any element numerically equal to the pivot will be in the correct positions in the array. Elements
+ * to their left are < them and elements to their right are > than them.
+ *
  * Complexity Analysis:
  * Time:
  * - Worst case (poor choice of pivot): O(n^2)

src/algorithms/sorting/quickSort/lomuto/QuickSort.java

@@ -0,0 +1 @@
+![ThreeWayPartitioning](../../../../../assets/ThreeWayPartitioning.jpeg)