Implement Three New Algorithms (#948)

* Create average_median.py

I created a program to calculate the median of a list of numbers.

* Changed Odd to Even in String

* Create decimal_to_binary.py

- Added 'conversions' folder.
- Created a decimal to binary converter.

* Implemented Decimal to Octal Algorithm

- I created a decimal to octal converter based on the converter in the TheAlgorithms/Python project.
- I added two newlines to make the output of decimal_to_binary.py better.

conversions/decimal_to_binary.py

@@ -0,0 +1,25 @@
+"""Convert a Decimal Number to a Binary Number."""
+
+
+def decimal_to_binary(num):
+    """Convert a Decimal Number to a Binary Number."""
+    binary = []
+    while num > 0:
+        binary.insert(0, num % 2)
+        num >>= 1
+    return "".join(str(e) for e in binary)
+
+
+def main():
+    """Print binary equivelents of decimal numbers."""
+    print("\n2 in binary is:")
+    print(decimal_to_binary(2))  # = 10
+    print("\n7 in binary is:")
+    print(decimal_to_binary(7))  # = 111
+    print("\n35 in binary is:")
+    print(decimal_to_binary(35))  # = 100011
+    print("\n")
+
+
+if __name__ == '__main__':
+    main()

conversions/decimal_to_octal.py

@@ -0,0 +1,38 @@
+"""Convert a Decimal Number to an Octal Number."""
+
+import math
+
+# Modified from:
+# https://github.com/TheAlgorithms/Javascript/blob/master/Conversions/DecimalToOctal.js
+
+
+def decimal_to_octal(num):
+    """Convert a Decimal Number to an Octal Number."""
+    octal = 0
+    counter = 0
+    while num > 0:
+        remainder = num % 8
+        octal = octal + (remainder * math.pow(10, counter))
+        counter += 1
+        num = math.floor(num / 8)  # basically /= 8 without remainder if any
+        # This formatting removes trailing '.0' from `octal`.
+    return'{0:g}'.format(float(octal))
+
+
+def main():
+    """Print octal equivelents of decimal numbers."""
+    print("\n2 in octal is:")
+    print(decimal_to_octal(2))  # = 2
+    print("\n8 in octal is:")
+    print(decimal_to_octal(8))  # = 10
+    print("\n65 in octal is:")
+    print(decimal_to_octal(65))  # = 101
+    print("\n216 in octal is:")
+    print(decimal_to_octal(216))  # = 330
+    print("\n512 in octal is:")
+    print(decimal_to_octal(512))  # = 1000
+    print("\n")
+
+
+if __name__ == '__main__':
+    main()

maths/average_median.py

@@ -0,0 +1,41 @@
+"""
+Find median of a list of numbers.
+
+Read more about medians:
+    https://en.wikipedia.org/wiki/Median
+"""
+
+
+def median(nums):
+    """Find median of a list of numbers."""
+    # Sort list
+    sorted_list = sorted(nums)
+    print("List of numbers:")
+    print(sorted_list)
+
+    # Is number of items in list even?
+    if len(sorted_list) % 2 == 0:
+        # Find index for first middle value.
+        mid_index_1 = len(sorted_list) / 2
+        # Find index for second middle value.
+        mid_index_2 = -(len(sorted_list) / 2) - 1
+        # Divide middle values by 2 to get average (mean).
+        med = (sorted_list[mid_index_1] + sorted_list[mid_index_2]) / float(2)
+        return med  # Return makes `else:` unnecessary.
+    # Number of items is odd.
+    mid_index = (len(sorted_list) - 1) / 2
+    # Middle index is median.
+    med = sorted_list[mid_index]
+    return med
+
+
+def main():
+    """Call average module to find median of a specific list of numbers."""
+    print("Odd number of numbers:")
+    print(median([2, 4, 6, 8, 20, 50, 70]))
+    print("Even number of numbers:")
+    print(median([2, 4, 6, 8, 20, 50]))
+
+
+if __name__ == '__main__':
+    main()