Add solution for Project Euler: Problem 89 (#2948)

* add solution for euler problem 89

* updates to accommodate euler solution guideline updates

* use more descriptive vars

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

DIRECTORY.md

@@ -717,6 +717,8 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_081/sol1.py)
   * Problem 087
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_087/sol1.py)
+  * Problem 089
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_089/sol1.py)
   * Problem 091
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_091/sol1.py)
   * Problem 097
@@ -735,10 +737,14 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_123/sol1.py)
   * Problem 125
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_125/sol1.py)
+  * Problem 129
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_129/sol1.py)
   * Problem 173
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_173/sol1.py)
   * Problem 174
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_174/sol1.py)
+  * Problem 188
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_188/sol1.py)
   * Problem 191
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_191/sol1.py)
   * Problem 203

project_euler/problem_089/__init__.py

@@ -0,0 +1 @@
+#

project_euler/problem_089/numeralcleanup_test.txt

@@ -0,0 +1,5 @@
+IIII
+IV
+IIIIIIIIII
+X
+VIIIII

project_euler/problem_089/sol1.py

@@ -0,0 +1,141 @@
+"""
+Project Euler Problem 89: https://projecteuler.net/problem=89
+
+For a number written in Roman numerals to be considered valid there are basic rules
+which must be followed. Even though the rules allow some numbers to be expressed in
+more than one way there is always a "best" way of writing a particular number.
+
+For example, it would appear that there are at least six ways of writing the number
+sixteen:
+
+IIIIIIIIIIIIIIII
+VIIIIIIIIIII
+VVIIIIII
+XIIIIII
+VVVI
+XVI
+
+However, according to the rules only XIIIIII and XVI are valid, and the last example
+is considered to be the most efficient, as it uses the least number of numerals.
+
+The 11K text file, roman.txt (right click and 'Save Link/Target As...'), contains one
+thousand numbers written in valid, but not necessarily minimal, Roman numerals; see
+About... Roman Numerals for the definitive rules for this problem.
+
+Find the number of characters saved by writing each of these in their minimal form.
+
+Note: You can assume that all the Roman numerals in the file contain no more than four
+consecutive identical units.
+"""
+
+import os
+
+SYMBOLS = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
+
+
+def parse_roman_numerals(numerals: str) -> int:
+    """
+    Converts a string of roman numerals to an integer.
+    e.g.
+    >>> parse_roman_numerals("LXXXIX")
+    89
+    >>> parse_roman_numerals("IIII")
+    4
+    """
+
+    total_value = 0
+
+    index = 0
+    while index < len(numerals) - 1:
+        current_value = SYMBOLS[numerals[index]]
+        next_value = SYMBOLS[numerals[index + 1]]
+        if current_value < next_value:
+            total_value -= current_value
+        else:
+            total_value += current_value
+        index += 1
+    total_value += SYMBOLS[numerals[index]]
+
+    return total_value
+
+
+def generate_roman_numerals(num: int) -> str:
+    """
+    Generates a string of roman numerals for a given integer.
+    e.g.
+    >>> generate_roman_numerals(89)
+    'LXXXIX'
+    >>> generate_roman_numerals(4)
+    'IV'
+    """
+
+    numerals = ""
+
+    m_count = num // 1000
+    numerals += m_count * "M"
+    num %= 1000
+
+    c_count = num // 100
+    if c_count == 9:
+        numerals += "CM"
+        c_count -= 9
+    elif c_count == 4:
+        numerals += "CD"
+        c_count -= 4
+    if c_count >= 5:
+        numerals += "D"
+        c_count -= 5
+    numerals += c_count * "C"
+    num %= 100
+
+    x_count = num // 10
+    if x_count == 9:
+        numerals += "XC"
+        x_count -= 9
+    elif x_count == 4:
+        numerals += "XL"
+        x_count -= 4
+    if x_count >= 5:
+        numerals += "L"
+        x_count -= 5
+    numerals += x_count * "X"
+    num %= 10
+
+    if num == 9:
+        numerals += "IX"
+        num -= 9
+    elif num == 4:
+        numerals += "IV"
+        num -= 4
+    if num >= 5:
+        numerals += "V"
+        num -= 5
+    numerals += num * "I"
+
+    return numerals
+
+
+def solution(roman_numerals_filename: str = "/p089_roman.txt") -> int:
+    """
+    Calculates and returns the answer to project euler problem 89.
+
+    >>> solution("/numeralcleanup_test.txt")
+    16
+    """
+
+    savings = 0
+
+    file1 = open(os.path.dirname(__file__) + roman_numerals_filename, "r")
+    lines = file1.readlines()
+    for line in lines:
+        original = line.strip()
+        num = parse_roman_numerals(original)
+        shortened = generate_roman_numerals(num)
+        savings += len(original) - len(shortened)
+
+    return savings
+
+
+if __name__ == "__main__":
+
+    print(f"{solution() = }")