rlishtaba
diff --git a/‎py_algorithms/challenges/various/quarantine/__init__.py
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diff --git a/‎py_algorithms/challenges/various/quarantine/arrays/__init__.py
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diff --git a/‎py_algorithms/challenges/various/quarantine/arrays/_sum_swap.py
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+29Lines changed: 29 additions & 0 deletions b/‎py_algorithms/challenges/various/quarantine/arrays/_sum_swap.py
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diff --git a/‎py_algorithms/challenges/various/quarantine/dp/__init__.py
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diff --git a/‎py_algorithms/challenges/various/quarantine/dp/_count_transformations.py
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+40Lines changed: 40 additions & 0 deletions b/‎py_algorithms/challenges/various/quarantine/dp/_count_transformations.py
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diff --git a/‎py_algorithms/challenges/various/quarantine/dp/_possible_change_ways.py
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+33Lines changed: 33 additions & 0 deletions b/‎py_algorithms/challenges/various/quarantine/dp/_possible_change_ways.py
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diff --git a/‎tests/py_algorithms/challenges/db/__init__.py
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@@ -0,0 +1,29 @@
+from typing import List
+from typing import Union
+
+
+def get_target(array1, array2):
+    sum1 = sum(array1)
+    sum2 = sum(array2)
+
+    if (sum1 - sum2) % 2 != 0:
+        return None
+    return (sum1 - sum2) // 2
+
+
+def algorithm(array1, array2) -> Union[None, List[tuple]]:
+    target = get_target(array1, array2)
+    if target is None:
+        return None
+    solutions = []
+    for x in array1:
+        for y in array2:
+            if x - y == target:
+                pair = (x, y,)
+                if pair not in solutions:
+                    solutions.append(pair)
+    return solutions
+
+
+if __name__ == '__main__':
+    assert algorithm([4, 1, 2, 1, 1, 2], [3, 6, 3, 3]) == [(4, 6), (1, 3)]
@@ -0,0 +1,40 @@
+from typing import Any
+
+
+class CountTransformations:
+    def __call__(self, a: str, b: str) -> Any:
+        n = len(a)
+        m = len(b)
+
+        if m == 0:
+            return 1
+
+        dp = [[0 for _ in range(n)] for _ in range(m)]
+
+        for i in range(0, m):
+            for j in range(i, n):
+                if i == 0:
+                    if a[j] == b[i] and j == 0:
+                        dp[i][j] = 1
+                    elif a[j] == b[i]:
+                        dp[i][j] = dp[i][j - 1] + 1
+                    else:
+                        dp[i][j] = dp[i][j - 1]
+                else:
+                    if a[j] == b[i]:
+                        dp[i][j] = dp[i][j - 1] + dp[i - 1][j - 1]
+                    else:
+                        dp[i][j] = dp[i][j - 1]
+        return dp[m - 1][n - 1]
+
+
+class TestCountTransformations:
+    def test_algorithm(self):
+        f = CountTransformations()
+        assert f(a="abcccdf", b="abccdf") == 3
+        assert f(a="aabba", b="ab") == 4
+
+
+if __name__ == '__main__':
+    runner = TestCountTransformations()
+    runner.test_algorithm()
@@ -0,0 +1,33 @@
+from typing import List
+
+
+def _make_change(amount: int, denoms: List[int], index: int, cache) -> int:
+    if amount in cache:
+        if index in cache[amount]:
+            return cache[amount][index]
+
+    if index >= len(denoms) - 1:
+        return 1
+
+    denom_amount = denoms[index]
+    ways = 0
+    i = 1
+    while i * denom_amount <= amount:
+        remaining = amount - i * denom_amount
+        ways += _make_change(remaining, denoms, index + 1, cache)
+        i += 1
+    if amount not in cache:
+        cache[amount] = {}
+    cache[amount][index] = ways
+
+    return ways
+
+
+def make_change(amount, denoms: List[int]):
+    cache = {}
+    ways = _make_change(amount, denoms, 0, cache)
+    return ways
+
+
+if __name__ == '__main__':
+    assert make_change(100, [1, 5, 10, 25]) == 2625