hihoCoder 1015KMP

Posted 2020-09-20 kimsimple

 

#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <math.h>
#include <string.h>
using namespace std;
#define N 2000010

char s[N],p[N];
int next1[N];
int kmp(char* s, char* p)
{
    int num=0;
    int i = 0;
    int j = 0;
    int sLen = strlen(s);
    int pLen = strlen(p);
    while (i < sLen && j < pLen)
    {
        if (j == -1 || s[i] == p[j])
        {
            i++;
            j++;
        }
        else
        {
            j = next1[j];
        }
        if(j==pLen) {
            num++;
            j = next1[j];
        }
    }

    return num;
}
///求部分匹配表
void GetKMPNext(char* p, int next[])
{
    int pLen = strlen(p);
    next1[0] = -1;
    int k = -1;
    int j = 0;
    while (j < pLen)  ///计算到0 - len
    {
        if (k == -1 || p[j] == p[k])
        {
            ++j;
            ++k;
            if (p[j] != p[k])
                next1[j] = k;
            else
                next1[j] = next1[k];
        }
        else
        {
            k = next1[k];
        }
    }
}


int main() {
    //freopen("input.txt","r",stdin);
    int T;
    scanf("%d",&T);
    while(T--){
        scanf("%s %s",p,s);  //p为模式串
        GetKMPNext(p,next1);
        printf("%d\n",kmp(s,p));
    }
    return 0;
}