Anthony Hart / Sorting

src/iterative_sorting/iterative_sorting.py

@@ -1,30 +1,36 @@
-# TO-DO: Complete the selection_sort() function below 
 def selection_sort( arr ):
-    # loop through n-1 elements
-    for i in range(0, len(arr) - 1):
-        cur_index = i
-        smallest_index = cur_index
-        # TO-DO: find next smallest element
-        # (hint, can do in 3 loc) 
-
-
-
-
-        # TO-DO: swap
-
+    for i in range(len(arr)-1):
+        sm_i = min(enumerate(arr[i:], start=i), key=lambda x: x[1])[0]
+        arr[i], arr[sm_i] = arr[sm_i], arr[i]
 
+    return arr
 
+def bubble_sort( arr ):
+    elem_num = len(arr)
+    sorted_elems = 0
+    while sorted_elems != elem_num:
+        for i in range(elem_num - sorted_elems - 1):
+            if arr[i] > arr[i+1]:
+                arr[i], arr[i+1] = arr[i+1], arr[i]
+        sorted_elems += 1
 
     return arr
 
+def count_sort( arr, maximum=-1 ):
+    if arr == []:
+        return []
 
-# TO-DO:  implement the Bubble Sort function below
-def bubble_sort( arr ):
+    if min(arr) < 0:
+        return 'Error, negative numbers not allowed in Count Sort'
 
-    return arr
+    cntArr = [0] * (max(arr)+1)
 
+    for e in arr:
+        cntArr[e]+=1
 
-# STRETCH: implement the Count Sort function below
-def count_sort( arr, maximum=-1 ):
+    index = 0
+    for i, e in enumerate(cntArr):
+        arr[index:index+e] = [i]*e
+        index+=e
 
-    return arr
+    return arr

src/iterative_sorting/test_iterative.py

@@ -26,16 +26,16 @@ def test_bubble_sort(self):
         self.assertEqual(bubble_sort(arr4), sorted(arr4))
 
     # Uncomment this test to test your count_sort implementation
-    # def test_counting_sort(self):
-    #     arr1 = [1, 5, 8, 4, 2, 9, 6, 0, 3, 7]
-    #     arr2 = []
-    #     arr3 = [1, 5, -2, 4, 3]
-    #     arr4 = random.sample(range(200), 50)
-
-    #     self.assertEqual(count_sort(arr1), [0,1,2,3,4,5,6,7,8,9])
-    #     self.assertEqual(count_sort(arr2), [])
-    #     self.assertEqual(count_sort(arr3), "Error, negative numbers not allowed in Count Sort")
-    #     self.assertEqual(count_sort(arr4), sorted(arr4))
+    def test_counting_sort(self):
+        arr1 = [1, 5, 8, 4, 2, 9, 6, 0, 3, 7]
+        arr2 = []
+        arr3 = [1, 5, -2, 4, 3]
+        arr4 = random.sample(range(200), 50)
+
+        self.assertEqual(count_sort(arr1), [0,1,2,3,4,5,6,7,8,9])
+        self.assertEqual(count_sort(arr2), [])
+        self.assertEqual(count_sort(arr3), "Error, negative numbers not allowed in Count Sort")
+        self.assertEqual(count_sort(arr4), sorted(arr4))
 
 
 if __name__ == '__main__':

src/recursive_sorting/recursive_sorting.py

@@ -2,16 +2,49 @@
 def merge( arrA, arrB ):
     elements = len( arrA ) + len( arrB )
     merged_arr = [0] * elements
-    # TO-DO
 
+    iM, iA, iB = 0, 0, 0
+    while iA < len( arrA ) and iB < len( arrB ):
+        if arrA[iA] < arrB[iB]:
+            merged_arr[iM] = arrA[iA]
+            iA += 1
+            iM += 1
+        else:
+            merged_arr[iM] = arrB[iB]
+            iB += 1
+            iM += 1
+
+    if iA == len( arrA ):
+        merged_arr[iM:] = arrB[iB:]
+    else:
+        merged_arr[iM:] = arrA[iA:]
+
     return merged_arr
 
 
 # TO-DO: implement the Merge Sort function below USING RECURSION
 def merge_sort( arr ):
-    # TO-DO
+    if arr == []:
+        return []
 
-    return arr
+    if not isinstance(arr[0], list):
+        arr = list(map(lambda x: [x], arr))
+
+    if len(arr) == 1:
+        return arr[0]
+
+    if len(arr) % 2 == 0:
+        split1 = arr[:len(arr)//2]
+        split2 = arr[len(arr)//2:]
+        rem = []
+    else:
+        split1 = arr[:len(arr)//2]
+        split2 = arr[len(arr)//2:-1]
+        rem = [arr[-1]]
+
+    merged = [ merge(a, b) for a, b in zip(split1, split2) ] + rem
+
+    return merge_sort(merged)
 
 
 # STRETCH: implement an in-place merge sort algorithm