zoj 3430 Detect the Virus（AC本身主動機）

Detect the Virus

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Time Limit: 2 Seconds       Memory Limit: 65536 KB

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One day, Nobita found that his computer is extremely slow. After several hours' work, he finally found that it was a virus that made his poor computer slow and the virus was activated by a misoperation of opening an attachment of an email.

Nobita did use an outstanding anti-virus software, however, for some strange reason, this software did not check email attachments. Now Nobita decide to detect viruses in emails by himself.

To detect an virus, a virus sample (several binary bytes) is needed. If these binary bytes can be found in the email attachment (binary data), then the attachment contains the virus.

Note that attachments (binary data) in emails are usually encoded in base64. To encode a binary stream in base64, first write the binary stream into bits. Then take 6 bits from the stream in turn, encode these 6 bits into a base64 character according the following table:

That is, translate every 3 bytes into 4 base64 characters. If the original binary stream contains 3k + 1 bytes, where k is an integer, fill last bits using zero when encoding and append '==' as padding. If the original binary stream contains 3k + 2 bytes, fill last bits using zero when encoding and append '=' as padding. No padding is needed when the original binary stream contains 3k bytes.

Value	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Encoding	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z	a	b	c	d	e	f
Value	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53	54	55	56	57	58	59	60	61	62	63
Encoding	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z	0	1	2	3	4	5	6	7	8	9	+	/

For example, to encode 'hello' into base64, first write 'hello' as binary bits, that is: 01101000 01100101 01101100 01101100 01101111
Then, take 6 bits in turn and fill last bits as zero as padding (zero padding bits are marked in bold): 011010 000110 010101 101100 011011 000110 111100
They are 26 6 21 44 27 6 60 in decimal. Look up the table above and use corresponding characters: aGVsbG8
Since original binary data contains 1 * 3 + 2 bytes, padding is needed, append '=' and 'hello' is finally encoded in base64: aGVsbG8=

Section 5.2 of RFC 1521 describes how to encode a binary stream in base64 much more detailedly:

Click here to see Section 5.2 of RFC 1521 if you have interest

Here is a piece of ANSI C code that can encode binary data in base64. It contains a function, encode (infile, outfile), to encode binary file infile in base64 and output result to outfile.

Click here to see the reference C code if you have interest

Input

Input contains multiple cases (about 15, of which most are small ones). The first line of each case contains an integer N (0 <= N <= 512). In the next N distinct lines, each line contains a sample of a kind of virus, which is not empty, has not more than 64 bytes in binary and is encoded in base64. Then, the next line contains an integer M (1 <= M <= 128). In the following M lines, each line contains the content of a file to be detected, which is not empty, has no more than 2048 bytes in binary and is encoded in base64.

There is a blank line after each case.

Output

For each case, output M lines. The i^th line contains the number of kinds of virus detected in the i^th file.

Output a blank line after each case.

Sample Input

3
YmFzZTY0
dmlydXM=
dDog
1
dGVzdDogdmlydXMu

1
QA==
2
QA==
ICAgICAgICA=

Sample Output

2

1
0

Hint

In the first sample case, there are three virus samples: base64, virus and t: , the data to be checked is test: virus., which contains the second and the third, two virus samples.

題意：給出n個編碼後的模板串，而後有M次詢問，每次詢問輸入一個編碼後的文本串。問在編碼前，有多少個模板串在文本串中出現過。

分析：我以爲這道題的難點不在於構建AC本身主動機。而在於怎樣把編碼後的字符串解碼成原文。編碼時先把字符串中的每一個字符轉化爲一個十進制整數。而後把每一個整數轉化爲8位2進制整數。而後把這些2進制數鏈接起來。從頭開始每次取6位，不足6位時在後邊補0，而後把這6位二進制轉化爲一個新的十進制整數。這個新的整數就是編碼後的字符的ASCII碼。編碼前的字符數量假設不是3的倍數，則在編碼後加入‘=’，數量爲字符數除以3的餘數。

 因爲解碼後的字符的ASCII值是從0~255的。因此最好不要用字符串存儲解碼後的內容。用int來保存較好一些。

#include<cstdio>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;

const int kind = 256; //the maximum number of letter
const int N = 50010;
struct Node
{
    int next[kind];
    int fail;
    int cnt;
    void build_node() {
        for(int i = 0; i < kind; i++)
            next[i] = 0;
        fail = 0;
        cnt = 0;
    }
} node[N];
int digit[N], code[N], Size, vis[N];
char file[N], vir[N];

int fun(char ch)  //convert char to int
{
    if(ch >= 'A' && ch <= 'Z') return ch - 'A';
    if(ch >= 'a' && ch <= 'z') return ch - 'a' + 26;
    if(ch >= '0' && ch <= '9') return ch - '0' + 52;
    if(ch == '+') return 62;
    return 63;
}

void change(char *str)
{
    int i, j, len, t;
    vector<int> v;
    memset(digit, 0, sizeof(digit));
    for(len = strlen(str); str[len-1] == '='; len--) ;
    str[len] = '\0';
    for(i = 0; i < len; i++)
        v.push_back(fun(str[i]));
    for(i = 0; i < v.size(); i++) {
        for(j = 6 * (i + 1) - 1; j >= 6 * i; j--) {
            if(v[i]&1)
                digit[j] = 1;
            v[i] >>= 1;
        }
    }
    int k = v.size() * 6 / 8; //the number of letter before encode
    for(i = 0; i < k; i++) {
        for(t = 0, j = 8 * i; j < 8 * (i + 1); j++)
            t = (t << 1) + digit[j];
        code[i] = t;
    }
    code[i] = -1;
}

void Insert()
{
    int cur, index, i;
    for(cur = i = 0; code[i] >= 0; i++) {
        index = code[i];
        if(node[cur].next[index] == 0) {
            node[++Size].build_node();
            node[cur].next[index] = Size;
        }
        cur = node[cur].next[index];
    }
    node[cur].cnt++;
}
void build_ac_automation(int root)
{
    queue<int> q;
    q.push(root);
    while(!q.empty()) {
        int cur = q.front(); q.pop();
        for(int i = 0; i < kind; i++) {
            if(node[cur].next[i]) {
                int p = node[cur].next[i];
                if(cur)
                    node[p].fail = node[node[cur].fail].next[i];
                q.push(p);
            }
            else
                node[cur].next[i] = node[node[cur].fail].next[i];
        }
    }
}
int Query()
{
    int ans = 0;
    for(int i = 0, cur = 0; code[i] >= 0; i++) {
        int index = code[i];
        cur = node[cur].next[index];
        for(int j = cur; j; j = node[j].fail) {
            if(!vis[j]) {
                ans += node[j].cnt;
                vis[j] = 1;
            }
        }
    }
    return ans;
}

int main()
{
    int n, m;
    while(~scanf("%d",&n)) {
        node[0].build_node();
        Size = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%s",vir);
            change(vir);
            Insert();
        }
        build_ac_automation(0);
        scanf("%d",&m);
        while(m--) {
            memset(vis, 0, sizeof(vis));
            scanf("%s", file);
            change(file);
            printf("%d\n", Query());
        }
        printf("\n");
    }
    return 0;
}