HDU-1686-Oulipo

链接：https://vjudge.net/problem/HDU-1686#author=0

题意：

求模式串在待匹配串的出现次数。

思路：

kmp

代码：

#include <iostream>
#include <memory.h>
#include <vector>
#include <map>
#include <algorithm>
#include <cstdio>
#include <math.h>
#include <queue>
#include <string>

using namespace std;

typedef long long LL;

const int MAXN = 1e6 + 10;
const int MAXM = 1e4 + 10;

int Next[MAXM];
string a, b;

void Get_Next(int m)
{
    int k = -1;
    int j = 0;
    Next[j] = k;
    while (j < m)
    {
        if (k == -1 || b[j] == b[k])
        {
            j++;
            k++;
            Next[j] = k;
        }
        else
            k = Next[k];
    }
}

int Kmp(int n, int m)
{
    int i = 0;
    int j = 0;
    int res = 0;
    Get_Next(m);
    while (i < n)
    {
        if (j == -1 || a[i] == b[j])
            i++, j++;
        else
            j = Next[j];
        if (j == m)
            res++;
    }
    return res;
}

int main()
{
    int t, n, m;
    cin >> t;
    while (t--)
    {
        memset(Next, 0, sizeof(Next));
        cin >> b >> a;
        cout << Kmp(a.length(), b.length()) << endl;
    }

    return 0;
}