from collections import defaultdict
input = """\
6,10
0,14
9,10
0,3
10,4
4,11
6,0
6,12
4,1
0,13
10,12
3,4
3,0
8,4
1,10
2,14
8,10
9,0
fold along y=7
fold along x=5"""
# with open("2021/day13/data.txt") as fh:
# input = fh.read()
dot_input, fold_input = input.split("\n\n")
pair_data = set()
for line in dot_input.splitlines():
x, y = line.split(",")
pair_data.add((int(x), int(y)))
# print(pair_data)
folds = []
for fold_line in fold_input.splitlines():
_, fold_val_str = fold_line.split("fold along ")
axis, fold_val = fold_val_str.split("=")
folds.append((0 if axis == "x" else 1, int(fold_val)))
# print(folds)
# part1 only the first fold
for axis, fold_val in folds[0:1]:
folded_pair_data = pair_data.copy()
for pair in pair_data:
point_val = pair[axis]
if point_val > fold_val:
folded_pair = list(pair)
folded_pair[axis] = 2 * fold_val - folded_pair[axis]
folded_pair_data.remove(pair)
folded_pair_data.add(tuple(folded_pair))
pair_data = folded_pair_data
print(len(folded_pair_data))
"""
0 0
1 1
2 2
3 3
4----
5 3 4 - (5-4) = n + -v +n = 2n-v
6 2 4 - (6-4)
7 1 4 - (7-4)
8 0 4 - (8-4)
"""
return_value = len(folded_pair_data)