Submission #64349162

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Source Code Expand

#include <iostream>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;

int main() {
    int t;
    cin >> t;

    while (t--) {
        int n; cin>>n;
        vector<int> arr(2*n);
        for(int i=0;i<2*n;i++) cin>>arr[i];

        vector<vector<int>> pos(n+1);

        for(int i=0;i<2*n;i++) pos[arr[i]].push_back(i);

        set<pair<int,int>> st;

        for(int i=0;i<2*n-1;i++) {
            if(arr[i] == arr[i+1]) {
                arr[i] = arr[i+1] = -1;
            }
        }

        for(int i=0;i<2*n-1;i++) {
            int a = arr[i], b = arr[i+1];
            if(a == -1 || b == -1) continue;
            int p1 = pos[a][0], p2 = pos[a][1];
            int p3 = pos[b][0], p4 = pos[b][1];

            vector<int> v{p1, p2, p3, p4};
            sort(v.begin(), v.end());

            if(v[0] + 1 == v[1] && v[2] + 1 == v[3]) {
                st.insert(minmax(a, b));
            }
        }

        cout<<st.size()<<endl;
    }
}

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