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时间:2015-03-13 22:20:02      阅读:220      评论:0      收藏:0      [点我收藏+]

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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。

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#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("]\n");
        }
    }
}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\n", a));
        }
        
        for (int j = 2; j >= 0; j--)
        {
            st2[i * 3 / 4 + j] = a % (1 << 8);
            a >>= 8;
            D(printf("**%d\n", 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\n", ac.query(st2));
    }
    puts("");
}

int main()
{

    while (scanf("%d", &n) != EOF)
    {
        ac.init();
        input();
    }
    return 0;
}
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zju3430

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原文地址:http://www.cnblogs.com/rainydays/p/4336073.html

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