Submission #5671961

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Source Code Expand

from collections import defaultdict, Counter


N, M = map(int, input().split())
x = list(map(int, input().split()))
x.sort()
c = Counter(x)
a = defaultdict(int)
E = defaultdict(int)
for i,j in c.items():
    a[i%M] += j
    E[i%M] += j//2
ans = a[0]//2
for i in range(1, M):
    j = M - i
    if i < j:
        m = min(a[i], a[j])
        t = min((a[i] - m)//2, E[i]) + min((a[j] - m)//2, E[j])
        ans += m+t
    elif i == j: #i==0は最初のifにかかってしまうため注意
        ans += a[i] //2

print(ans)

Submission Info

Judge Result