Improve power.py (#12567)

* Fix And Add power.py

To fix the inaccuracies and allow handling of negative exponents and bases, the key issue lies in how negative numbers are handled in the power calculation, especially when dividing.
## Example Output:
```python
>>> power(4, 6)
4096
>>> power(2, 3)
8
>>> power(-2, 3)
-8
>>> power(2, -3)
0.125
>>> power(-2, -3)
-0.125
```

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* Update power.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update power.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update power.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update power.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>

divide_and_conquer/power.py

@@ -1,4 +1,4 @@
-def actual_power(a: int, b: int):
+def actual_power(a: int, b: int) -> int:
     """
     Function using divide and conquer to calculate a^b.
     It only works for integer a,b.
@@ -19,10 +19,12 @@ def actual_power(a: int, b: int):
     """
     if b == 0:
         return 1
+    half = actual_power(a, b // 2)
+
     if (b % 2) == 0:
-        return actual_power(a, int(b / 2)) * actual_power(a, int(b / 2))
+        return half * half
     else:
-        return a * actual_power(a, int(b / 2)) * actual_power(a, int(b / 2))
+        return a * half * half
 
 
 def power(a: int, b: int) -> float:
@@ -43,9 +45,9 @@ def power(a: int, b: int) -> float:
     -0.125
     """
     if b < 0:
-        return 1 / actual_power(a, b)
+        return 1 / actual_power(a, -b)
     return actual_power(a, b)
 
 
 if __name__ == "__main__":
-    print(power(-2, -3))
+    print(power(-2, -3))  # output -0.125