classic clear solution for Similar Triangles by kdim - python coding challenges

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classic solution in Clear category for Similar Triangles by kdim

from typing import List, Tuple
from math import sqrt
Coords = List[Tuple[int, int]]

def lenxy(a):
    return (a[1][0]-a[0][0])**2+(a[1][1]-a[0][1])**2


def similar_triangles(coords_1: Coords, coords_2: Coords) -> bool:
    s1 = sorted([ lenxy([coords_1[i], coords_1[(i+1)%3] ]) for i in (0,1,2) ])
    s2 = sorted([ lenxy([coords_2[i], coords_2[(i+1)%3] ]) for i in (0,1,2) ])
    s = [l1/l2 for l1, l2 in zip(s1,s2)]
    return s[0] == s[-1]


if __name__ == '__main__':
    print("Example:")
    print(similar_triangles([(0, 0), (1, 2), (2, 0)], [(3, 0), (4, 2), (5, 0)]))

    # These "asserts" are used for self-checking and not for an auto-testing
    assert similar_triangles([(0, 0), (1, 2), (2, 0)], [(3, 0), (4, 2), (5, 0)]) is True, 'basic'
    assert similar_triangles([(0, 0), (1, 2), (2, 0)], [(3, 0), (4, 3), (5, 0)]) is False, 'different #1'
    assert similar_triangles([(0, 0), (1, 2), (2, 0)], [(2, 0), (4, 4), (6, 0)]) is True, 'scaling'
    assert similar_triangles([(0, 0), (0, 3), (2, 0)], [(3, 0), (5, 3), (5, 0)]) is True, 'reflection'
    assert similar_triangles([(1, 0), (1, 2), (2, 0)], [(3, 0), (5, 4), (5, 0)]) is True, 'scaling and reflection'
    assert similar_triangles([(1, 0), (1, 3), (2, 0)], [(3, 0), (5, 5), (5, 0)]) is False, 'different #2'
    print("Coding complete? Click 'Check' to earn cool rewards!")

Jan. 3, 2021

Comments:

vvm70 on April 1, 2021, 2:07 a.m.
You import math but don't use it

jakubbortlik on Nov. 23, 2022, 10:42 a.m.
I would find the code more readable if `lenxy()` would accept two arguments, lets say `def lenxy(a, b): (b[0]-a[0])2+(b[1]-a[1])2` and `s1 = sorted(lenxy(coords1[i], coords1[(i+1)%3]) for i in (0,1,2))`. Note that you can leave out the square brackets in list comprehensions which are immediately consumed by a function like `sorted([x for x in range(10)])`, then you in fact use a generator expressions instead: `sorted(x for x in range(10))`. The output is the same but you may save some memory when the full list is not created first. And you also save some extra characters and probably enhance readability :)

dig on March 15, 2023, 7:35 p.m.
When I did this challenge I was expecting it must had been shorter. Now reeding your code I see it with kind of the same idea but doing effective shorter than mine. Thanks for sharing :)

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