test: add check to max counters challenge

lesson4/max_counters.py

@@ -1,39 +1,57 @@
 """
-class MaxCounter:
-    def solution(self, N: int, A: List[int]) -> List[int]:
+lesson learned: The operation to update all values in the array when a max counter operation is performed is time consuming
+So this solution it's really slow when the number of elements in the array is big
+
+def solution(self, N: int, A: List[int]) -> List[int]:
+
+    counters = N * [0]
+
+    for posi, elem in enumerate(A):
+        if elem == N + 1:
+            counters[:] = len(counters) * [max(counters)]
+            continue
+        counters[elem - 1] += 1
+
+    return counters
+
+Another solution is to keep track of the min value and the max value,
+and only apply the max operation over the counters at the end of the loop
+This way we can avoid the time consuming operation of updating all the values in the array
+
+First iteration:
+[0 0 0 0 0] init max=0 min=0
+[0 0 1 0 0] 3 - max=0 min=0; get_max(min, p[3]) = 0 + 1 = 1 ; max = 1
+[0 0 1 1 0] 4 - max=1 min=0; get_max(min, p[4]) = 0 + 1 = 1 ; max = 1
+[0 0 1 2 0] 4 - max=1 min=0; get_max(min, p[4]) = 1 + 1 = 2 ; max = 2
+[0 0 1 2 0] 6 - max=2 min=2 not apply the max operation over the counters, just update the min value with the max value
+[3 0 1 2 0] 1 - max=2 min=2; get_max(min, p[1]) = 2 + 1 = 3 ; max = 3
+[3 0 1 3 2] 4 - max=2 min=2; get_max(min, p[4]) = 2 + 1 = 3 ; max = 3
+[3 0 1 4 0] 4 - max=3 min=2; get_max(min, p[4]) = 3 + 1 = 4 ; max = 4
+
+Last iteration:
+min = 2
+[3 0 1 4 0] 1 - max=4 min=2; p[1] = get_max(min, p[1]) = 3
+[3 2 1 4 0] 2 - max=4 min=2; p[2] = get_max(min, p[2]) = 2
+[3 2 2 4 0] 3 - max=4 min=2; p[3] = get_max(min, p[3]) = 2
+[3 2 2 4 0] 4 - max=4 min=2; p[4] = get_max(min, p[4]) = 4
+[3 2 2 4 0] 5 - max=4 min=2; p[5] = get_max(min, p[5]) = 2
 
-        counters = N * [0]
-
-        for posi, elem in enumerate(A):
-            if elem == N + 1:
-                counters[:] = len(counters) * [max(counters)]
-                continue
-            counters[elem - 1] += 1
-
-        return counters
 """
-from typing import List
-
-
-class MaxCounter:
-    def solution(self, N: int, A: List[int]) -> List[int]:
 
-        counters = N * [0]
-        length_counters = len(counters)
-        maximum_value = 0
 
-        for elem in A:
-            if elem == N + 1:
-                counters[:] = length_counters * [maximum_value]
-                continue
-            counters[elem - 1] += 1
-            if maximum_value < counters[elem - 1]:
-                maximum_value = counters[elem - 1]
+async def solution(counters_dim: int, operations: list[int]) -> list[int]:
+    """Returns the final state of the counters after applying the operations"""
+    min_value, max_value = 0, 0
+    counters = counters_dim * [0]
 
-        return counters
+    for elem in operations:
+        if elem == counters_dim + 1:
+            min_value = max_value
+            continue
+        counters[elem - 1] = max(min_value, counters[elem - 1]) + 1
+        max_value = max(max_value, counters[elem - 1])
 
+    for index in range(counters_dim):
+        counters[index] = max(min_value, counters[index])
 
-if __name__ == "__main__":
-    num = 5
-    sample = [3, 4, 4, 6, 1, 4, 4]
-    print(MaxCounter().solution(num, sample))
+    return counters

tests/lesson4/test_max_counters.py

@@ -0,0 +1,19 @@
+import pytest
+
+from lesson4.max_counters import solution
+
+
+@pytest.mark.parametrize(
+    "counters_dim, operations, expected",
+    [
+        (5, [3, 4, 4, 6, 1, 4, 4], [3, 2, 2, 4, 2]),
+    ],
+)
+@pytest.mark.asyncio
+async def test_max_counters_is_working(
+    counters_dim: int,
+    operations: list[int],
+    expected: list[int],
+):
+    """Should return the final state of the counters after applying the operations"""
+    assert await solution(counters_dim, operations) == expected