HDU 1686：Oulipo ← KMP算法（重叠计算）

【题目来源】
http://acm.hdu.edu.cn/showproblem.php?pid=1686
http://poj.org/problem?id=3461

【题目描述】
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.

【输入格式】
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.

【输出格式】
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.

【输入样例】
3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

【输出样例】
1
3
0

【算法分析】
1.常规定义的 KMP 函数，第一个参数为主串，第二个参数为模式串，但是本题中给出的样例是先输入模式串，再输入主串。故在本题中调用定义的 KMP 函数时，要注意参数顺序。
2.本题中统计的是模式串在主串中重叠出现的次数。
故在 KMP 函数中，把在 if(j==lent) 时，不重叠进行统计时的 j=0 修改为重叠进行统计时的 j=ne[j]。例如：
题目“HDU 2087：剪花布条”，不重叠计算模式串在主串中出现的次数。（if(j==lent), j=0）
题目“HDU 1686：Oulipo”，重叠计算模式串在主串中出现的次数。（if(j==lent), j=ne[j]）
3.实证知在 HDU 中不支持对 string 求长度，故可将如下代码中的 string 修改为字符数组后再提交至 HDU 进行测试。但是要注意，字符数组 x 的长度用 strlen(x) 进行计算，字符串 x 的长度用 x.length() 进行计算。

【算法代码：string版本】
本 string 版本代码是正确的，但是在 HDU 上不能通过测试，原因是 HDU 无法识别 string。

#include
using namespace std;

const int maxn=1e4+5;
int ne[maxn];

void getNext(string t) {
    int len=t.length();
    int i=0, j=-1;
    ne[0]=-1;
    while(i>T;
    while(T--) {
        string s,t;
        cin>>s>>t;
        getNext(t);
        cout<

【算法代码：字符数组版本】
本字符数组版本代码，在 HDU 上可正常通过测试。此字符数组版本代码，只是在 string 版本代码基础上做了微改。

#include 
#include 
using namespace std;

const int maxn=1e6+5;
char s[maxn];
char t[maxn];
int ne[maxn];

void getNext(char t[]) {
    int len=strlen(t);
    int i=0, j=-1;
    ne[0]=-1;
    while(i>T;
    while(T--) {
        cin>>s>>t;
        getNext(t);
        cout<

【参考文献】
https://blog.csdn.net/hnjzsyjyj/article/details/127112363
https://blog.csdn.net/hnjzsyjyj/article/details/127140892
https://blog.csdn.net/hnjzsyjyj/article/details/127112363
https://blog.csdn.net/Ezereal/article/details/50998678