799. 最长连续不重复子序列

#include<iostream>
#include<algorithm>
using namespace std;
const int N = 1000010;
int a[N],s[N];
int n;

int main(){
    scanf("%d",&n);

    for(int i = 1 ; i <= n ; i ++) scanf("%d",&a[i]);

    int res = 0;
    for(int i = 0 , j = 0 ; i < n ; i ++){
        //j为大循环
        s[a[i]]++；
        while(j < i && s[a[i]] > 1) s[a[j++]]--;
        res = max(res,i-j+1);
    }
    cout << res;
}