UVa 11572 (滑动窗口) Unique Snowflakes

滑动窗口挺有意思的，如果符合条件右端点一直向前走，不符合的话，左端点向前走。

#include <bits/stdc++.h>
using namespace std;

set<int> Set;

const int maxn = 1000000 + 10;
int a[maxn];

int Scan() {    //输入外挂
    int res = 0;
    char ch;
    while((ch = getchar()) >= '0' && ch <= '9')
        res = res * 10 + (ch - '0');
    return res;
}

int main()
{
    //freopen("in.txt", "r", stdin);
    int T, n;
    scanf("%d", &T);
    while(T--)
    {
        Set.clear();
        scanf("%d", &n); getchar();
        for(int i = 0; i < n; ++i) a[i] = Scan();
        int L = 0, R = 0, ans = 0;
        for(; L < n; ++L)
        {
            while(R < n &&!Set.count(a[R])) { Set.insert(a[R]); R++; }
            ans = max(ans, R - L);
            if(R == n) break;
            Set.erase(a[L]);
        }
        printf("%d
", ans);
    }

    return 0;
}