[双指针、模拟]最长连续不重复子序列

模拟即可（

#include <iostream>
using namespace std;
const int maxn = 2e5 + 10;

int n, a[maxn];
int vis[maxn];

int main() {
    scanf("%d", &n);
    int l = 1, r = 0, ans = 0;
    for (int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);
        r++;
        vis[a[r]]++;
        while (l < r && vis[a[r]] > 1) {
            vis[a[l]]--;
            l++;
        }
        ans = max(ans, r - l + 1);
        //for (int i = l; i <= r; i++) printf("%d ", a[i]); printf("\n");
    }
    printf("%d", ans);
    return 0;
}