Merge pull request #33 from ikostan/exercism-sync/2d8e06b48072e81b

[Sync Iteration] python/triangle/1

Author: ikostan

solutions/python/triangle/1/triangle.py

@@ -0,0 +1,49 @@
+"""Determine if a triangle is equilateral, isosceles, or scalene."""
+
+
+def equilateral(sides: list) -> bool:
+    """
+    An equilateral triangle has all three sides the same length.
+    """
+    if check_for_zeroes(sides) and inequality_violation(sides):
+        return sides[0] == sides[1] == sides[2]
+    return False
+
+
+def isosceles(sides: list) -> bool:
+    """
+    An isosceles triangle has at least two sides the same length.
+    (It is sometimes specified as having exactly two sides the same length,
+    but for the purposes of this exercise we'll say at least two.)
+    """
+    if check_for_zeroes(sides) and inequality_violation(sides):
+        return sides[0] == sides[1] or sides[1] == sides[2] or sides[0] == sides[2]
+    return False
+
+
+def scalene(sides: list) -> bool:
+    """
+    A scalene triangle has all sides of different lengths.
+    """
+    if check_for_zeroes(sides) and inequality_violation(sides):
+        return sides[0] != sides[1] and sides[1] != sides[2] and sides[0] != sides[2]
+    return False
+
+
+def inequality_violation(sides: list) -> bool:
+    """
+    Let a, b, and c be sides of the triangle.
+    Then all three of the following expressions must be true:
+
+    a + b ≥ c
+    b + c ≥ a
+    a + c ≥ b
+    """
+    return sides[0] + sides[1] >= sides[2] and sides[0] + sides[2] >= sides[1] and sides[2] + sides[1] >= sides[0]
+
+
+def check_for_zeroes(sides: list) -> bool:
+    """No zeroes allowed."""
+    if 0 in sides:
+        return False
+    return True