超级读入挂HDU（6044）

#include <cstdio>
#include <cstring>
#include <algorithm>
typedef long long LL;
namespace fastIO {
    #define BUF_SIZE 100000
    //fread -> read
    bool IOerror = 0;
    inline char nc() {
        static char buf[BUF_SIZE], *p1 = buf + BUF_SIZE, *pend = buf + BUF_SIZE;
        if(p1 == pend) {
            p1 = buf;
            pend = buf + fread(buf, 1, BUF_SIZE, stdin);
            if(pend == p1) {
                IOerror = 1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t';
    }
    inline void read(int &x) {
        char ch;
        while(blank(ch = nc()));
        if(IOerror)
            return;
        for(x = ch - '0'; (ch = nc()) >= '0' && ch <= '9'; x = x * 10 + ch - '0');
    }
    #undef BUF_SIZE
};
using namespace fastIO;
const int maxn = 1000001, mod = 1000000007;
int fact[maxn], iact[maxn];
int n, l[maxn], r[maxn], ord[maxn], pL[maxn], pR[maxn], sz[maxn], tmp[maxn];
int bfs(int rt)
{
    int L = 0, R = 0;
    static int que[maxn], f[maxn];
    que[R++] = rt;
    while(L < R)
    {
        int u = que[L++], vL = pL[u], vR = pR[u];
        // [L, R] at x -> [L, x-1] [x+1, R]
        if(l[u] == u)
        {
            if(vL != -1)
                return 0;
        }
        else
        {
            if(vL == -1 || vL >= u || r[vL] != u - 1)
                return 0;
            que[R++] = vL;
        }
        if(u == r[u])
        {
            if(vR != -1)
                return 0;
        }
        else
        {
            if(vR == -1 || vR <= u || l[vR] != u + 1)
                return 0;
            que[R++] = vR;
        }
    }
    for(int i = n - 1; i >= 0; --i)
    {
        int u = que[i], ret = 1, szL, szR;
        if(l[u] == u)
            szL = 0;
        else
        {
            ret = (LL)ret * f[pL[u]] % mod;
            szL = sz[pL[u]];
        }
        if(u == r[u])
            szR = 0;
        else
        {
            ret = (LL)ret * f[pR[u]] % mod;
            szR = sz[pR[u]];
        }
        if(szL && szR)
            ret = (LL)ret * fact[szL + szR] % mod * iact[szL] % mod * iact[szR] % mod;
        sz[u] = szL + szR + 1;
        f[u] = ret;
    }
    return f[rt];
}
int main()
{
    iact[1] = 1;
    for(int i = 2; i < maxn; ++i)
        iact[i] = mod - (int)(mod / i * (LL)iact[mod % i] % mod);
    fact[0] = iact[0] = 1;
    for(int i = 1; i < maxn; ++i)
    {
        fact[i] = (LL)fact[i - 1] * i % mod;
        iact[i] = (LL)iact[i - 1] * iact[i] % mod;
    }
    for(int Case = 1; read(n), !fastIO::IOerror; ++Case)
    {
        for(int i = 1; i <= n; ++i)
            read(l[i]);
        for(int i = 1; i <= n; ++i)
            read(r[i]);
        ord[0] = ord[n + 1] = 0;
        int *cnt = sz;
        memset(cnt + 1, 0, n * sizeof(int));
        for(int i = 1; i <= n; ++i)
            ++cnt[r[i]];
        for(int i = 2; i <= n; ++i)
            cnt[i] += cnt[i - 1];
        for(int i = n; i >= 1; --i)
            tmp[cnt[r[i]]--] = i;
        memset(cnt + 1, 0, n * sizeof(int));
        for(int i = 1; i <= n; ++i)
            ++cnt[l[i]];
        for(int i = 2; i <= n; ++i)
            cnt[i] += cnt[i - 1];
        for(int i = n; i >= 1; --i)
            ord[cnt[l[tmp[i]]]--] = tmp[i];
        for(int i = 1; i <= n; ++i)
            pL[ord[i]] = l[ord[i - 1]] == l[ord[i]] ? ord[i - 1] : -1;
        memset(cnt + 1, 0, n * sizeof(int));
        for(int i = 1; i <= n; ++i)
            ++cnt[l[i]];
        for(int i = 2; i <= n; ++i)
            cnt[i] += cnt[i - 1];
        for(int i = n; i >= 1; --i)
            tmp[cnt[l[i]]--] = i;
        memset(cnt + 1, 0, n * sizeof(int));
        for(int i = 1; i <= n; ++i)
            ++cnt[r[i]];
        for(int i = 2; i <= n; ++i)
            cnt[i] += cnt[i - 1];
        for(int i = n; i >= 1; --i)
            ord[cnt[r[tmp[i]]]--] = tmp[i];
        for(int i = 1; i <= n; ++i)
            pR[ord[i]] = r[ord[i]] == r[ord[i + 1]] ? ord[i + 1] : -1;
        int pos = -1;
        for(int i = 1; i <= n; ++i)
            if(l[i] == 1 && r[i] == n)
            {
                pos = i;
                break;
            }
        printf("Case #%d: %d\n", Case, pos == -1 ? 0 : bfs(pos));
    }
    return 0;
}