基础KMP两道

1. HDU 1711 Number Sequence  

代码：

#include <iostream>

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

using namespace std;

#define N 10007



int a[1000007],b[N],next[N];

int n,m;



void getnext()

{

    next[0] = -1;

    int i = 0,j = -1;

    while(i<m)

    {

        if(j == -1 || b[i] == b[j])

        {

            ++i,++j;

            if(b[i] != b[j])

                next[i] = j;

            else

                next[i] = next[j];

        }

        else

            j = next[j];

    }

}



int kmp()

{

    int i = -1,j = -1;

    while(i<n && j<m)

    {

        if(j == -1 || a[i] == b[j])

            i++,j++;

        else

            j = next[j];

    }

    if(j == m)

        return i-j+1;

    return 0;

}



int main()

{

    int t,i,res;

    scanf("%d",&t);

    while(t--)

    {

        scanf("%d%d",&n,&m);

        for(i=0;i<n;i++)

            scanf("%d",&a[i]);

        for(i=0;i<m;i++)

            scanf("%d",&b[i]);

        if(n<m)

        {

            printf("-1\n");

            continue;

        }

        getnext();

        res = kmp();

        if(res)

            printf("%d\n",res);

        else

            printf("-1\n");

    }

    return 0;

}

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代码2：

#include <iostream>

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

using namespace std;

#define N 10007



int a[1000007],b[N],next[N];

int n,m;



void getnext()

{

    next[0] = -1;

    int i = 0,j = -1;

    while(i<m-1)

    {

        if(j == -1 || b[i] == b[j])

            next[++i] = ++j;

        else

            j = next[j];

    }

}



int kmp()

{

    int i = -1,j = -1;

    while(i<n && j<m)

    {

        if(j == -1 || a[i] == b[j])

            i++,j++;

        else

            j = next[j];

    }

    if(j == m)

        return i-j+1;

    return 0;

}



int main()

{

    int t,i,res;

    scanf("%d",&t);

    while(t--)

    {

        scanf("%d%d",&n,&m);

        for(i=0;i<n;i++)

            scanf("%d",&a[i]);

        for(i=0;i<m;i++)

            scanf("%d",&b[i]);

        if(n<m)

        {

            printf("-1\n");

            continue;

        }

        getnext();

        res = kmp();

        if(res)

            printf("%d\n",res);

        else

            printf("-1\n");

    }

    return 0;

}

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2.POJ 3461 Oulipo

代码：

#include <iostream>

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

using namespace std;

#define N 10007



char a[1000004],b[N];

int next[N];

int n,m,cnt;



void getnext()

{

    next[0] = -1;

    int i = 0,j = -1;

    while(i<m)

    {

        if(j == -1 || b[i] == b[j])

            next[++i] = ++j;

        else

            j = next[j];

    }

}



void kmp()

{

    int i = -1,j = -1;

    while(i<n && j<m)

    {

        if(j == -1 || a[i] == b[j])

            i++,j++;

        else

            j = next[j];

        if(j == m)

        {

            cnt++;

            j = next[j];

        }

    }

}



int main()

{

    int t,i;

    scanf("%d",&t);

    while(t--)

    {

        scanf("%s",b);

        scanf("%s",a);

        n = strlen(a);

        m = strlen(b);

        getnext();

        cnt = 0;

        kmp();

        printf("%d\n",cnt);

    }

    return 0;

}

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