chore: add recursion factorial C++ and Python (#413)

algorithms/CPlusPlus/README.md

@@ -108,3 +108,4 @@
 # Recursion
 
 1. [Tower of Hanoi](Recursion/towerofHanoi.cpp)
+2. [Factorial](Recursion/factorial.cpp)

algorithms/CPlusPlus/Recursion/factorial.cpp

@@ -0,0 +1,32 @@
+/*******************
+ * August 09, 2021
+ * Leo Nugraha
+ * Factorial problems via recursive or non-recursive methods
+ * Run: g++ -std=c++11 factorial.cpp -o factorial
+ ******************/
+#include <iostream>
+
+int FactorialNonRecursion(int number) {
+  int result = 1;
+  for (int i=1; i<number+1; ++i)
+    result = result * i;
+  return result;
+}
+
+int FactorialRecursion(int number) {
+  if (number == 0 || number == 1) {
+    return 1;
+  }
+  return number * FactorialRecursion(number-1);
+}
+
+int main(int argc, char *argv[]){
+
+  int testNonRecursion = FactorialNonRecursion(5);
+  std::cout << testNonRecursion << "\n";
+
+  int testRecursion = FactorialRecursion(3);
+  std::cout << testRecursion << "\n";
+
+  return 0;
+}

algorithms/Python/README.md

@@ -16,6 +16,10 @@
 
 1. [Karatsuba](multiplication/karatsuba.py)
 
+## Recursion
+
+1. [Factorial](recursion/factorial.py)
+
 ## Scheduling
 
 1. [Interval Scheduling](scheduling/interval_scheduling.py)

algorithms/Python/recursion/factorial.py

@@ -0,0 +1,52 @@
+def FactorialNonRecursion(number):
+    """
+    >>> FactorialNonRecursion(3)
+    6
+    >>> FactorialNonRecursion(5)
+    120
+    >>> FactorialNonRecursion(0)
+    1
+    >>> FactorialNonRecursion(1)
+    1
+    """
+    if isinstance(number, float):
+        raise ValueError("Non integer number is not allowed")
+    if number < 0:
+        raise ValueError("Negative number is not allowed") # Raise an error here
+    if number == 0 or number == 1:
+        return 1
+
+    result = 1
+    for i in range(1, number+1):
+        result = result * i
+    return result
+
+def FactorialRecursion(number):
+    """
+    >>> FactorialRecursion(3)
+    6
+    >>> FactorialRecursion(5)
+    120
+    >>> FactorialRecursion(0)
+    1
+    >>> FactorialRecursion(1)
+    1
+    """
+    if isinstance(number, float) is True:
+        raise ValueError("Non integer number is not allowed")
+    if number < 0:
+        raise ValueError("Negative number is not allowed")
+    if number == 0 or number == 1:
+        return 1
+
+    return number * FactorialRecursion(number-1)
+
+def main():
+    testFactorial = FactorialNonRecursion(5)
+    print(testFactorial)
+
+    testRecursion = FactorialRecursion(4)
+    print(testRecursion)
+
+if __name__ == "__main__":
+    main()