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  • zju3430

    题意:给出多个加密的模式串,和多个待匹配的串,问每个串里出现了多少种模式串。加密方法是把每3bytes加密成按6bits一个对应成4个字符,对应方法题里给了。

    分析:除了解密之外,基本是个赤裸裸的AC自动机。这题要注意有多个模式串要进自动机,所以自动机的vis数组要每次清零。

    #include <cstdio>
    #include <queue>
    #include <cstring>
    #include <cctype>
    using namespace std;
    
    #define D(x) 
    
    const int MAX_CHILD_NUM = 256;
    const int MAX_NODE_NUM = 100 * 512 + 10;
    const int MAX_LEN = 3000 + 10;
    
    char st[MAX_LEN];
    int st2[MAX_LEN];
    bool vis[MAX_NODE_NUM];
    
    struct Trie
    {
        int next[MAX_NODE_NUM][MAX_CHILD_NUM];
        int fail[MAX_NODE_NUM];
        int count[MAX_NODE_NUM];
        int node_cnt;
        int root;
    
        void init()
        {
            node_cnt = 0;
            root = newnode();
        }
    
        int newnode()
        {
            for (int i = 0; i < MAX_CHILD_NUM; i++)
                next[node_cnt][i] = -1;
            count[node_cnt++] = 0;
            return node_cnt - 1;
        }
    
        int get_id(int a)
        {
            return a;
        }
    
        void insert(int buf[], int id)
        {
            int now = root;
            for (int i = 0; buf[i] != -1; i++)
            {
                int id = get_id(buf[i]);
                if (next[now][id] == -1)
                    next[now][id] = newnode();
                now = next[now][id];
            }
            count[now]++;
        }
    
        void build()
        {
            queue<int>Q;
            fail[root] = root;
            for (int i = 0; i < MAX_CHILD_NUM; i++)
                if (next[root][i] == -1)
                    next[root][i] = root;
                else
                {
                    fail[next[root][i]] = root;
                    Q.push(next[root][i]);
                }
            while (!Q.empty())
            {
                int now = Q.front();
                Q.pop();
                for (int i = 0; i < MAX_CHILD_NUM; i++)
                    if (next[now][i] == -1)
                        next[now][i] = next[fail[now]][i];
                    else
                    {
                        fail[next[now][i]]=next[fail[now]][i];
                        Q.push(next[now][i]);
                    }
            }
        }
    
        int query(int buf[])
        {
            int now = root;
            int res = 0;
            for (int i = 0; buf[i] != -1; i++)
            {
                now = next[now][get_id(buf[i])];
                int temp = now;
                while (temp != root && !vis[temp])
                {
                    res += count[temp];
                     // optimization: prevent from searching this fail chain again.
                    //also prevent matching again.
                    vis[temp] = true;
                    temp = fail[temp];
                }
            }
            return res;
        }
    
        void debug()
        {
            for(int i = 0;i < node_cnt;i++)
            {
                printf("id = %3d,fail = %3d,end = %3d,chi = [",i,fail[i],count[i]);
                for(int j = 0;j < MAX_CHILD_NUM;j++)
                    printf("%2d",next[i][j]);
                printf("]
    ");
            }
        }
    }ac;
    
    int n, m;
    
    int get_value(char ch)
    {
        if (isupper(ch))
            return ch - 'A';
        if (islower(ch))
            return ch - 'a' + 26;
        if (isdigit(ch))
            return ch - '0' + 52;
        if (ch == '+')
            return 62;
        return 63;
    }
    
    void transform(char *st, int *st2)
    {
        int len = strlen(st);
        int len2 = len * 3 / 4;
        for (int i = 0; i < len; i += 4)
        {
            int a = 0;
            for (int j = 0; j < 4; j++)
            {
                    a = (a << 6) + get_value(st[i + j]);
                D(printf("**%d
    ", a));
            }
            
            for (int j = 2; j >= 0; j--)
            {
                st2[i * 3 / 4 + j] = a % (1 << 8);
                a >>= 8;
                D(printf("**%d
    ", st2[i * 3 / 4 + j]));
            }
        }
        while (st[len - 1] == '=')
        {
            len--;
            len2--;
        }
        st2[len2] = -1;
        D(puts("#"));
        for (int i = 0; i < len2; i++)
        {
            D(printf("%d ", st2[i]));
        }
        D(puts(""));
    }
    
    void input()
    {
        for (int i = 1; i <= n; i++)
        {
            scanf("%s", st);
            transform(st, st2);
            ac.insert(st2, i);
        }
        ac.build();
        scanf("%d", &m);
        for (int i = 0; i < m; i++)
        {
            scanf("%s", st);
            transform(st, st2);
            memset(vis, 0, sizeof(vis));
            printf("%d
    ", ac.query(st2));
        }
        puts("");
    }
    
    int main()
    {
    
        while (scanf("%d", &n) != EOF)
        {
            ac.init();
            input();
        }
        return 0;
    }
    View Code
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  • 原文地址:https://www.cnblogs.com/rainydays/p/4336073.html
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