poj 3461 Oulipo__演算法之kmp

題意：求一個子串在主串出現的個數，可以重疊。直接kmp計數，i不回溯，j在next數組上回溯。

#include<cstdio>#include<cstring>#include<cstdlib>#include<climits>#include<stack>#include<queue>#include<iostream>#include<algorithm>using namespace std;char S[1000010],T[10010];int next[10010];void get_next(char *s,int *next){    memset(next,0,sizeof(next));    next[0]=-1;    int i=0,j=-1;    int len=strlen(s);    while(i<len)    {        if(j==-1||s[i]==s[j])        {            i++,j++;            next[i]=j;        }        else            j=next[j];    }}int main(){    int n;scanf("%d",&n);    while(n--)    {        scanf("%s %s",T,S);        get_next(T,next);        int len=strlen(S),L=strlen(T);        int ans=0;        for(int i=0,j=0;i<len;)        {            if(S[i]==T[j]||j==-1)            {                i++,j++;                if(j==L) {ans++,j=next[j];}            }            else j=next[j];        }        printf("%d\n",ans);    }}