POJ 3461 KMP

题目链接

题意：

给定S串和T串，求S串在T串内的出现次数。

思路：

KMP模板题。

C++代码：

#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<queue>
#include<vector>
#include<string>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 1000010;

int Nx[maxn];
char S[maxn];
char T[maxn];

void GetKmpNext( char *s , int *nx )
{
    nx[0] = -1;
    int len = strlen(s);
    for ( int i=0,j=-1 ; i<len ; i++ )
    {
        while ( j!=-1&&s[i]!=s[j] )
            j = nx[j];
        nx[i+1] = ++j;
    }
}

int Kmp( char *a , char *b , int *nx )
{
    int res = 0;
    int la = strlen(a);
    int lb = strlen(b);
    GetKmpNext( b , nx );
    for ( int i=0,j=0 ; i<la ; i++ )
    {
        while ( j!=-1&&a[i]!=b[j] )
            j = nx[j];
        if ( ++j==lb ) res++;
    }
    return res;
}

int main()
{
    int Cas; scanf ( "%d" , &Cas );
    while ( Cas-- )
    {
        scanf ( "%s%s" , S , T );
        printf ( "%d\n" , Kmp( T , S , Nx ) );
    }
    return 0;
}