用每个点之间的距离查找点的顺序

Question

I'm coding a program that finds the order of three (can be more) points on a linear line using the distance between the points.

For example, if the input is a .txt file as below:

A,A,0
A,B,57
A,C,43
B,B,0
B,C,100
C,C,0

The output should be:

['B','A','C'] 

I am having a hard time finding an algorithm that would make this work. It would be of so much help if you guys can give me some insight.

Answer 1

This is a generic solution that should work for any number of points:

distance_input = """A,A,0
A,B,57
A,C,43
B,B,0
B,C,100
C,C,0"""

# Convert the input string to more sane data structures
distances = {tuple(sorted(s.split(",")[:2])): int(s.split(",")[-1]) for s in distance_input.splitlines()}
point_list = [s.split(",")[0] for s in distance_input.splitlines()]
points = {}

# The min (or max) is one of the points in the pair that has the highest distance
max_distance = max(distances.items(), key=lambda t: t[1])
min_point = max_distance[0][0]
points[min_point] = 0

# Calculate remaining values using their distances from 0
for point in point_list:
    points[point] = distances[tuple(sorted([point, min_point]))]

ordering = [p for p, v in sorted(points.items(), key=lambda t: t[1])]
print(ordering)

This will print

['B', 'A', 'C']

Answer 2

First, let's get the distance between A and B, A and C, and B and C, as that's what interests us.

filename = "text.txt" # Change this to the name of your file
file = open("file.txt", "r")
lines = file.readLines()

for line in lines: # Read every line in the file one by one
    data = line.split(",") # Separate the line by comma
    # data[0] is the first point, data[1] is the second, and data[2] is the distance
    if data[0] == "A" and data[1] == "B":
        a_to_b = int(data[2])
    elif data[0] == "A" and data[1] == "C":
        a_to_c = int(data[2])
    elif data[0] == "B" and data[1] == "C":
        b_to_c = int(data[2])

Next, you can use that to figure out the order of the points:

if a_to_b == a_to_c + b_to_c:
    order = ["A", "C", "B"]
elif a_to_c == a_to_b + b_to_c:
    order = ["A", "B", "C"]
elif b_to_c == a_to_b + a_to_c:
    order = ["B", "A", "C"]

Finally, close the file:

file.close()

This only works for 3 points, but hopefully it can get you started.