题解— HDU 1686 Oulipo (KMP算法)

题目链接：https://cn.vjudge.net/contest/388654#status/2019030001040/B/0/

字符串匹配 KMP模板题

#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <string>
#include <cmath>
#include <vector>
#include <queue>

using namespace std;
typedef long long ll;

char str[1000005], pattern[10005];
int Next[10005];
int cnt;

void getFail(char* p, int plen)
{
    Next[0] = 0, Next[1] = 0;
    for (int i = 1; i < plen; i++)
    {
        int j = Next[i];
        while (j && p[i] != p[j]) j = Next[j];
        Next[i + 1] = (p[i] == p[j]) ? j + 1 : 0;
    }

}

void kmp(char* s, char* p)
{
    int last = -1;
    int slen = strlen(s), plen = strlen(p);
    getFail(p, plen);
    int j = 0;
    for (int i = 0; i < slen; i++)
    {
        while (j && s[i] != p[j]) j = Next[j];
        if (s[i] == p[j]) j++;
        if (j == plen)
        {
            cnt++;
            last = i;
        }
    }
}

int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        scanf("%s", pattern);
        scanf("%s", str);
        cnt = 0;
        kmp(str, pattern);
        printf("%d\n", cnt);
    }
    return 0;
}