直接手写队列+哈希

#include<iostream>

#define N 1010
using namespace std;

int n,m;
int t[N*N];

int main()
{
    cin>>n>>m;
    int q[N*N];
    int hh = 0 , tt = 0;
    int res = 0;
    while(m --)
    {
        int a;
        cin>>a;

        if(t[a])    continue;

        if(tt < n)
        {
            res ++;
            q[tt ++] = a;
            t[a] = true;
            continue;
        }

        if(tt - hh == n)
        {
            t[q[hh ++]] = false;
            res ++;
            q[tt ++] = a;
            t[a] = true;
        }

    }

    cout<<res<<endl;
    return 0;
}