Sorting

src/iterative_sorting/iterative_sorting.py

@@ -2,15 +2,19 @@
 def selection_sort( arr ):
     # loop through n-1 elements
     for i in range(0, len(arr) - 1):
-        cur_index = i
+        cur_index = i #
         smallest_index = cur_index
-        # TO-DO: find next smallest element
+        # TO-DO: find next smallest element, (x, y = y, x)
         # (hint, can do in 3 loc) 
-
-
+        for j in range(cur_index, len(arr)):
+            if arr[j] < arr[smallest_index]:
+                smallest_index = j     
 
 
         # TO-DO: swap
+        temp = arr[smallest_index]
+        arr[smallest_index] = arr[cur_index]
+        arr[cur_index] = temp
 
 
 
@@ -19,12 +23,17 @@ def selection_sort( arr ):
 
 
 # TO-DO:  implement the Bubble Sort function below
-def bubble_sort( arr ):
-
+def bubble_sort(arr):
+    n = len(arr)
+    for i in range(n - 1):
+        # For each element in the array...
+        for j in range(n - 1 - i):
+            # Check it's neighbor to the right...
+            if arr[j] > arr[j + 1]:
+                # If neighbor is smaller, swap and make Flag true
+                arr[j], arr[j + 1] = arr[j + 1], arr[j]
     return arr
 
-
 # STRETCH: implement the Count Sort function below
 def count_sort( arr, maximum=-1 ):
-
     return arr

src/recursive_sorting/recursive_sorting.py

@@ -1,15 +1,54 @@
 # TO-DO: complete the helpe function below to merge 2 sorted arrays
+# We are only comparing the first elements of the arrays, as they are already sorted
 def merge( arrA, arrB ):
     elements = len( arrA ) + len( arrB )
     merged_arr = [0] * elements
     # TO-DO
-
+    # Initialise pointers for the front of Arrays A & B
+    a = 0
+    b = 0
+    for i in range(0, elements):
+        # compare thearrays
+         if a >= len(arrA):    # all elements in arrA have been merged
+            merged_arr[i] = arrB[b]
+            b += 1
+        elif b >= len(arrB):  # all elements in arrB have been merged
+            merged_arr[i] = arrA[a]
+            a += 1
+        elif arrA[a] < arrB[b]:  # next element in arrA smaller, so add to final array
+            merged_arr[i] = arrA[a]
+            a += 1
+        else:  # else, next element in arrB must be smaller, so add it to final array
+            merged_arr[i] = arrB[b]
+            b += 1
     return merged_arr
 
 
+def merge(arrA, arrB):
+    elements = len(arrA) + len(arrB)
+    merged_arr = [0] * elements
+    a = 0
+    b = 0
+    # since arrA and arrB already sorted, we only need to compare the first element of each when merging!
+    for i in range(0, elements):
+
+
+
 # TO-DO: implement the Merge Sort function below USING RECURSION
 def merge_sort( arr ):
     # TO-DO
+    def merge_sort( arr ):
+        if len(arr) > 1:
+            # split the array
+            mid = len(arr) // 2
+            # split again - left
+            left = arr[:mid]
+            # split again - right
+            right = arr[mid:]
+            arr = merge(left, right)
+
+        mergeSort(left)
+        mergeSort(right)
 
     return arr