Oulipo (HDU - 1686)
题面
The French author Georges Perec (1936–1982) once wrote a book, La disparition, without the letter ’e’. He was a member of the Oulipo group. A quote from the book:
Tout avait Pair normal, mais tout s’affirmait faux. Tout avait Fair normal, d’abord, puis surgissait l’inhumain, l’affolant. Il aurait voulu savoir où s’articulait l’association qui l’unissait au roman : stir son tapis, assaillant à tout instant son imagination, l’intuition d’un tabou, la vision d’un mal obscur, d’un quoi vacant, d’un non-dit : la vision, l’avision d’un oubli commandant tout, où s’abolissait la raison : tout avait l’air normal mais…
Perec would probably have scored high (or rather, low) in the following contest. People are asked to write a perhaps even meaningful text on some subject with as few occurrences of a given “word” as possible. Our task is to provide the jury with a program that counts these occurrences, in order to obtain a ranking of the competitors. These competitors often write very long texts with nonsense meaning; a sequence of 500,000 consecutive ‘T’s is not unusual. And they never use spaces.
So we want to quickly find out how often a word, i.e., a given string, occurs in a text. More formally: given the alphabet {‘A’, ‘B’, ‘C’, …, ‘Z’} and two finite strings over that alphabet, a word W and a text T, count the number of occurrences of W in T. All the consecutive characters of W must exactly match consecutive characters of T. Occurrences may overlap.
输入
The first line of the input file contains a single number: the number of test cases to follow. Each test case has the following format:
One line with the word W, a string over {‘A’, ‘B’, ‘C’, …, ‘Z’}, with 1 ≤ |W| ≤ 10,000 (here |W| denotes the length of the string W). One line with the text T, a string over {‘A’, ‘B’, ‘C’, …, ‘Z’}, with |W| ≤ |T| ≤ 1,000,000.
输出
For every test case in the input file, the output should contain a single number, on a single line: the number of occurrences of the word W in the text T.
样例输入
13
2BAPC
3BAPC
4AZA
5AZAZAZA
6VERDI
7AVERDXIVYERDIAN
样例输出
11
23
30
提示
无
思路
KMP模板题
代码
1char s[mxn], t[mxn];
2int nxt[mxn];
3
4void getnxt(char* t, int m)
5{
6 int i = 0, j = -1; nxt[0] = -1;
7 while (i < m)
8 {
9 if (j == -1 || t[i] == t[j]) {
10 i++, j++;
11 // if (t[i] == t[j])
12 // nxt[i] = nxt[j]; // next数组优化
13 // else
14 nxt[i] = j;
15 } else
16 j = nxt[j];
17 }
18}
19
20int KMP(char* s, char* t, int n, int m)
21{
22 int i = 0, j = 0, ans = 0;
23 while (i < n)
24 {
25 if (j == -1 || s[i] == t[j]) {
26 i++, j++;
27 if (j >= m) { // 匹配
28 ans++;
29 j = nxt[j];
30 // return i-j;
31 }
32 } else
33 j = nxt[j];
34 }
35 return ans;
36 // return -1;
37}
38
39int main()
40{
41 int T; scanf("%d", &T);
42 while(T--)
43 {
44 scanf("%s%s", t, s);
45 int tl = strlen(t), sl = strlen(s);
46 getnxt(t, tl);
47 printf("%d\n", KMP(s, t, sl, tl));
48 }
49 return 0;
50}