例题8-7　唯一的雪花（Unique snowflakes, UVa 11572）

#include <set>
#include <map>
#include <ctime>
#include <cmath>
#include <stack>
#include <queue>
#include <deque>
#include <cstdio>
#include <string>
#include <vector>
#include <cctype>
#include <sstream>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#define SF(a) scanf("%d", &a)
#define PF(a) printf("%d\n", a)
#define SFF(a, b) scanf("%d%d", &a, &b)
#define SFFF(a, b, c) scanf("%d%d%d", &a, &b, &c)
#define SFFFF(a, b, c, d) scanf("%d%d%d%d", &a, &b, &c, &d)
#define CLEAR(a, b) memset(a, b, sizeof(a))
#define IN() freopen("in.txt", "r", stdin)
#define OUT() freopen("out.txt", "w", stdout)
#define FOR(i, a, b) for(int i = a; i < b; ++i)
#define LL long long
#define maxn 1000005
#define maxm 205
#define mod 1000000007
#define INF 10000007
#define eps 1e-4
using namespace std;
//-------------------------CHC------------------------------//
int a[maxn];
set<int> s;

int main() {
int T, n;
SF(T);
while (T--) {
s.clear();
SF(n);
FOR(i, 0, n) SF(a[i]);
int l = 0, r = 0, ans = 0;
while (r < n) {
if (s.count(a[r]) == 0) s.insert(a[r++]);
else s.erase(a[l++]);
ans = max(ans, r - l);
}
PF(ans);
}
return 0;
}