Submission #68349046

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Source Code Expand

from collections import Counter, defaultdict
from itertools import combinations
from math import gcd


N = int(input())
XY = []
for _ in range(N):
    x, y = map(int, input().split())
    XY.append((x, y))
XY.sort()
countl = Counter()
countd = defaultdict(lambda: defaultdict(int))

SIZE = 1 << 30


def conv(x, y):
    return SIZE * x + y


for (x1, y1), (x2, y2) in combinations(XY, 2):
    x = x2 - x1
    y = y2 - y1
    if x == 0:
        countl[conv(0, 1)] += 1
        countd[conv(0, 1)][y * y] += 1
    elif y == 0:
        countl[conv(1, 0)] += 1
        countd[conv(1, 0)][x * x] += 1
    else:
        d = x * x + y * y
        g = abs(gcd(x, y))
        x //= g
        y //= g

        countl[conv(x, y)] += 1
        countd[conv(x, y)][d] += 1
ans = 0
dup = 0
for v, t in countl.items():
    ans += t * (t - 1) // 2
    for t2 in countd[v].values():
        dup += t2 * (t2 - 1) // 2

print(ans - dup // 2)

Submission Info

Judge Result