solved: practice #2 merge_sort algorithm -@iamserda

neetcodeio/algostructybeginners/Lv3-Sorting/merge_sort_solution2.py

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+import math, random
+
+
+def merge_sort(arr):
+    """sorts an array, in ascending order"""
+    if not arr:
+        print(ValueError("List is empty. Cannot sort an empty list."))
+        return []
+
+    if len(arr) == 1:
+        return arr
+    else:
+        mid = int(math.ceil(len(arr) / 2))
+        arr1 = merge_sort(arr[:mid])
+        arr2 = merge_sort(arr[mid:])
+        arr3 = merge_sorted_arrays(arr1, arr2)
+        return arr3
+
+
+def merge_sorted_arrays(sorted_arr1, sorted_arr2):
+    sorted_arr3 = []
+    i = 0
+    j = 0
+    while True:
+        if i >= len(sorted_arr1) and j >= len(sorted_arr2):
+            return sorted_arr3
+
+        if i < len(sorted_arr1) and j >= len(sorted_arr2):
+            sorted_arr3.append(sorted_arr1[i])
+            i += 1
+            continue
+
+        if j < len(sorted_arr2) and i >= len(sorted_arr1):
+            sorted_arr3.append(sorted_arr2[j])
+            j += 1
+            continue
+
+        if sorted_arr1[i] <= sorted_arr2[j]:
+            sorted_arr3.append(sorted_arr1[i])
+            i += 1
+            continue
+
+        if sorted_arr1[i] > sorted_arr2[j]:
+            sorted_arr3.append(sorted_arr2[j])
+            j += 1
+            continue
+        break
+    return sorted_arr3
+
+
+# Testing Arenas:
+
+arr = [random.randint(-10, 10) for i in range(10)]
+print("before:", arr)
+sorted_arr = merge_sort(arr)
+sorted_arr_prime = sorted(arr)
+assert sorted_arr == sorted_arr_prime
+print("after:", sorted_arr)