HDU 1686 Oulipo

题目：http://acm.hdu.edu.cn/showproblem.php?pid=1686

 

大意：求模式串在主串出现的次数。。（可以重复）

 

#include <iostream>
#include <string>
using namespace std;

const int L1 = 1000010;
const int L2 = 10010;


char s[L1], p[L2];
int nxt[L2], l1, l2;
int  res;

void GetNext()
{
    int k = -1, j = 0;
    nxt[0] = -1;
    while (j < l2)
    {
        if (k == -1 || p[j] == p[k])
        {
            j++, k++;
            if (p[j] != p[k])
            {
                nxt[j] = k;
            }
            else
            {
                nxt[j] = nxt[k];
            }
        }
        else
        {
            k = nxt[k];    
        }
    }
}


int Kmp(int pos)
{
    int i = pos, j = 0;
    while (i < l1 && j < l2)
    {
        if (j == -1 || s[i] == p[j])
        {
            i++, j++;
        }
        else
        {
            j = nxt[j];
        }
        if (j == l2)
        {
            res++;
            j = nxt[j];
        }
    }
    return res;
}


int main()
{
    int t;
    int i;
    scanf("%d", &t);
    
    while (t--)
    {

        scanf("%s%s", p, s);
        l1 = strlen(s);
        l2 = strlen(p);
        GetNext();
        res = 0;
        printf("%d\n", Kmp(0));
        
    }
    
    return 0;
}