feat: add docs for bubble and insertion sort (alexfertel#44)

Author: JoelStanleyD

src/sorting/bubble_sort.rs

@@ -1,5 +1,10 @@
+// It sorts the array by repeatedly comparing the adjacent elements and swapping them if they are in the wrong order
+// Time complexity is O(N^2)
+// Auxiliary space is O(1)
+
 pub fn bubble_sort<T: Ord>(array: &mut [T]) {
     for i in 0..array.len() {
+        // Last i elements are already in place
         for j in 0..array.len() - 1 - i {
             if array[j] > array[j + 1] {
                 array.swap(j, j + 1);

src/sorting/insertion_sort.rs

@@ -1,6 +1,16 @@
+// Insertion sort divides the array into sorted and unsorted parts.
+// Values from the unsorted parts are placed in the correct position in the sorted part
+// time complexity is O(N^2)
+// Auxiliary space is O(1)
+
 pub fn insertion_sort<T: Ord>(array: &mut [T]) {
+    // initialise the array
     for i in 0..array.len() {
         let mut j = i;
+        // Move elements of arr[0..i-1],  
+        // that are greater than key, to one 
+        // position ahead of their 
+        // current position
         while j > 0 && array[j] < array[j - 1] {
             array.swap(j, j - 1);
             j -= 1;