UVa11572 Unique Snowflakes (滑动窗口)

链接：http://vjudge.net/problem/UVA-11572

分析：维护一个set即可。

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <set>
 4 using namespace std;
 5
 6 const int maxn = 1000000 + 5;
 7
 8 int n, a[maxn];
 9
10 int main() {
11     int T;
12     scanf("%d", &T);
13     while (T--) {
14       scanf("%d", &n);
15       for (int i = 0; i < n; i++) scanf("%d", &a[i]);
16       set<int> s;
17       int L = 0, R = 0, ans = 0;
18       while (R < n) {
19         while (R < n && !s.count(a[R])) s.insert(a[R++]);
20         ans = max(ans, R - L);
21         s.erase(a[L++]);
22       }
23       printf("%d\n", ans);
24     }
25     return 0;
26 }