``` #include <bits/stdc++.h> #define objl '\n' typedef long long ll; using namespace std; //数据结构在这里定义 const int N = 1e6 + 10; int arr[N]; int n,x; ////区间是否不重复 //超时了 //bool valid(int s, int e){ // set<int> tmp; // for(int i = s;i<=e;i++){ // if(tmp.find(arr[i])!=tmp.end()) // return false; // tmp.insert(arr[i]); // } // return true; //} void solve(){ cin >> n; for(int i = 1;i<=n;i++){ cin >> arr[i]; } //滑动窗口 int maxlen = -1; int start_id = 1; map<int, int> tmp;//帮助去重 for(int end_id = 1; end_id <=n; end_id++){ //for循环开始时 arr[end_id]加入了子序列,让序列变长 tmp[arr[end_id]]++; //验证是否符合不重复要求 //最长子序列，只有不满足条件才考虑移动start_id //如果是最短，那只要满足条件就移动start_id while(tmp[arr[end_id]]>1){ //重复了，说明子序列太长了，右移start_id缩短 //直到重新满足不重复 tmp[arr[start_id]]--; start_id++; } //此时满足不重复，更新长度 maxlen = max(maxlen, end_id - start_id + 1); } cout << maxlen << endl; } int main(){ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); int t;//多组数据要cin //cin >> t; t = 1; while(t--){ solve(); } return 0;//必须加return 0 } ```

``` #include <bits/stdc++.h> using namespace std; const int N = 100010; int a[N]; int cnt[N]; int n; int main(){ scanf("%d",&n); for (int i = 1; i <= n; ++i) { scanf("%d",&a[i]); } int res = -1; for (int i = 1,j = 1; i <= n; ++i) { cnt[a[i]]++; while(j <= i && cnt[a[i]] > 1) { cnt[a[j]]--; ++j; } res = max(res,i - j + 1); } printf("%d\n",res); return 0; } ```

``` #include <bits/stdc++.h> using namespace std; const int N = 100010; int a[N]; int cnt[N]; int n; int main(){ scanf("%d",&n); for (int i = 1; i <= n; ++i) { scanf("%d",&a[i]); } int res = -1; for (int i = 1,j = 1; i <= n; ++i) { cnt[a[i]]++; while(j <= i && cnt[a[i]] > 1) { cnt[a[j]]--; ++j; } res = max(res,i - j + 1); } printf("%d\n",res); return 0; } ```