Create check_polygon.py (#4605)

* Create check_polygon.py

* Update check_polygon.py

* Update maths/check_polygon.py

* Update check_polygon.py

* Update check_polygon.py

Co-authored-by: John Law <johnlaw.po@gmail.com>

maths/check_polygon.py

@@ -0,0 +1,31 @@
+from typing import List
+
+
+def check_polygon(nums: List) -> bool:
+    """
+    Takes list of possible side lengths and determines whether a
+    two-dimensional polygon with such side lengths can exist.
+
+    Returns a boolean value for the < comparison
+    of the largest side length with sum of the rest.
+    Wiki: https://en.wikipedia.org/wiki/Triangle_inequality
+
+    >>> check_polygon([6, 10, 5])
+    True
+    >>> check_polygon([3, 7, 13, 2])
+    False
+    >>> check_polygon([])
+    Traceback (most recent call last):
+        ...
+    ValueError: List is invalid
+    """
+    if not nums:
+        raise ValueError("List is invalid")
+    nums.sort()
+    return nums.pop() < sum(nums)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()