HDU 5763

KMP，预处理nxt，然后去文本串中匹配，f[i]表示前i个字母有多少种意思，当匹配到i成功时，说明i-len+1.....i可以表达为2种意思，所以f[i]=f[i-1]+f[i-len]。想了许久，暴露了我的sb智商

#include<cstdio>#include<cstring>#define maxl 100010#define mod 1000000007int cas,tlen,slen;int f[maxl],nxt[maxl];char t[maxl],s[maxl];void getnxt(){int j=0;nxt[1]=0;for(int i=2;i<=tlen;i++){while(j && t[j+1]!=t[i])j=nxt[j];if(t[j+1]==t[i])j++;nxt[i]=j;}}void prework(){scanf("%s%s",s+1,t+1);tlen=strlen(t+1);slen=strlen(s+1);getnxt();}void mainwork(){f[0]=1;int j=0;for(int i=1;i<=slen;i++){f[i]=f[i-1];while(j && t[j+1]!=s[i])j=nxt[j];if(t[j+1]==s[i])j++;if(j==tlen)f[i]=(f[i]+f[i-tlen])%mod;}}void print(){printf("Case #%d: %d\n",cas,f[slen]);}int main(){int tot;scanf("%d",&tot);for(cas=1;cas<=tot;cas++){prework();mainwork();print();}return 0;}