POJ 3461 Oulipo (KMP)

Oulipo

Time Limit: 1000MS Memory Limit: 65536KTotal Submissions: 36043 Accepted: 14548

Description

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.

Input

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.

Output

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.

Sample Input

3BAPCBAPCAZAAZAZAZAVERDIAVERDXIVYERDIAN

Sample Output

130

题意：给你两个字符串t和s，求出t在s中出现的次数

#include <cstdio>#include <cstring>using namespace std;const int maxn = 1000000 + 10;char s[maxn], t[maxn];int next[maxn];int lens, lent;int ans;void getNext(){    int i = 0, j = -1;    next[0] = -1;    while (i != lent){        if (j == -1 || t[i] == t[j]){    //这里写成s[i] == s[j] 也可以过，why？？            next[++i] = ++j;        }        else{            j = next[j];        }    }}int KMP(){    int i = 0, j = 0, count = 0;    while (i != lens && j != lent){        if (s[i] == t[j] || j == -1){            ++i;            ++j;        }        else            j = next[j];        if (j == lent){            count++;            j = next[j];        }    }    return count;}int main(){    int n;    scanf("%d", &n);    while (n--){        scanf("%s%s", t, s);        lent = strlen(t);        lens = strlen(s);        getNext();        ans = KMP();        printf("%d\n", ans);    }    return 0;}