1956B - Nene and the Card Game - CodeForces Solution

import math
from collections import Counter
def solve(n,a):
    c=Counter(a)
    ans=0
    for x in c:
        if c[x]==2: ans+=1
    return ans
for _ in range(int(input())):
            n=int(input())
    a=list(map(int,input().split()))
    print(solve(n,a))