B. A BIT of a Construction.cpp

#include <bits/stdc++.h>
#define int long long
#define vi vector<int>
#define vb vector<bool>
#define readInput(a) \
  for (auto &i : a)  \
  cin >> i
#define printOutput(a) \
  for (auto &i : a)    \
  cout << i << " "
#define endLine "\n"
#define space << " " <<
#define pushBack pb
#define allElements(a) a.begin(), a.end()
#define reverseAll(a) a.rbegin(), a.rend()
const int N = 1e6 + 2;
const int MOD = 1e9 + 7;
const int INF = LLONG_MAX;
using namespace std;

signed main()
{
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t; cin >> t;

  while (t--) {

    int n, k; cin >> n ;
    vector<int> arr(n);

    set<int> se;

    for (int i = 0; i <n; i++)
    {
      /* code */
      cin>>arr[i];

      se.insert(arr[i]);
    }


    cout<<n-se.size()<<endl;


    


    
  }
}




/*


class Solution:
    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
    # map each course to prereq list
        preMap ={ i:[] for i in range(numCourses)}
        for crs, pre in prerequisites:
            preMap[crs].append(pre)

        # visitSet = all courses along the curr DFS path
        visitSet = set()
        def dfs(crs):
            if crs in visitSet:
                return False
            if preMap[crs] == []:
                return True

            visitSet.add(crs)
            for pre in preMap[crs]:
                if not dfs(pre): return False
            visitSet.remove(crs)
            preMap[crs] = []
            return True

        for crs in range(numCourses):
            if not dfs(crs): return False
        return True


*/