原题链接：https://vjudge.net/problem/UVA-11572
分类：滑动窗口
备注：双指针
#include<bits/stdc++.h>
using namespace std;
const int maxn=1e6+5;
map<int,int>vis;
int t,n,a[maxn];
int main(void){// freopen("in.txt","r",stdin);// freopen("out.txt","w",stdout);scanf("%d",&t);while(t--){int ans=0; vis.clear();scanf("%d",&n);for(int i=1;i<=n;i++)scanf("%d",&a[i]);int R=1,len=0;for(int L=1;L<=n;vis[a[L]]=0,L++,len--){while(R<=n&&!vis[a[R]]){vis[a[R]]=1; R++; len++;}if(len>ans)ans=len;while(L<R&&a[L]!=a[R]){vis[a[L]]=0; L++; len--;}}printf("%d\n",ans);}return 0;
}