UVa 11572 唯一的雪花

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

const int maxn = 1000000 + 5;
int a[maxn];
int n;


int maxd;

void solve()
{
    set<int> num;
    int L = 0, R = 0;
    maxd = 0;
    int ans = 0;
    while (R < n)
    {
        if (!num.count(a[R]))
        {
            ans++;
            num.insert(a[R]);
            R++;
            if (ans>maxd)  maxd = ans;
        }
        else
        {
            num.erase(a[L]);
            ans--;
            L++;
        }
    }
}

int main()
{
    //freopen("D:\\txt.txt", "r", stdin);
    int t;
    cin >> t;
    while (t--)
    {
        cin >> n;
        for (int i = 0; i < n; i++)
        {
            cin >> a[i];
        }
        solve();
        cout << maxd << endl;
    }
    return 0;
}