【bzoj1009】: [HNOI2008]GT考试 字符串-kmp-矩阵乘法-DP

【bzoj1009】: [HNOI2008]GT考试

先用kmp写个暴力

 /* http://www.cnblogs.com/karl07/ */
 #include <cstdlib>
 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 using namespace std;
 char s[];
 int n,m,p,fail[],f[][];

 void kmp(){
     fail[]=;
     for (int i=;i<=m;i++){
         fail[i]=fail[i-];
         if (s[fail[i-]]==s[i-]) fail[i-]=fail[fail[i-]];
         while (s[fail[i]]!=s[i-] && fail[i]) fail[i]=fail[fail[i]];
         fail[i]++;
     }
 }

 int main(){
     scanf("%d%d%d",&n,&m,&p);
     scanf("%s",s+);
     kmp();
     f[][]=;
     for (int i=;i<=n;i++){
         for (int j=;j<m;j++){
             for (int k='',now=j+;k<='';k++,now=j+){
                 while (k!=s[now] && now) now=fail[now];
                 f[i][now]=(f[i][now]+f[i-][j])%p;
             }
         }
     }
     int ans=;
     for (int i=;i<m;i++){
         ans=(ans+f[n][i])%p;
     }
     printf("%d\n",ans);
     return ;
 }

暴力

然后对着转移方程yy一下矩阵就好辣

 /* http://www.cnblogs.com/karl07/ */
 #include <cstdlib>
 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <algorithm>
 using namespace std;
 char s[];
 int n,m,p,fail[];
 struct MAT{
     int m[][];
     int x,y;
 }m1,m2;

 MAT operator * (const MAT &a,const MAT &b){
     MAT c;
     c.x=b.x,c.y=a.y;
     for (int i=;i<=c.x;i++){
         for (int j=;j<=c.y;j++){
             c.m[i][j]=;
             for (int k=;k<=b.y;k++){
                 c.m[i][j]=(c.m[i][j]+a.m[k][j]*b.m[i][k])%p;
             }
         }
     }
     return c;
 }

 int sum(MAT a){
     int ans=;
     for (int i=;i<=a.x;i++){
         for (int j=;j<=a.y;j++){
             ans=(ans+a.m[i][j])%p;
         }
     }
     return ans;
 }

 void kmp(){
     fail[]=;
     for (int i=;i<=m;i++){
         fail[i]=fail[i-];
         if (s[fail[i-]]==s[i-]) fail[i-]=fail[fail[i-]];
         while (s[fail[i]]!=s[i-] && fail[i]) fail[i]=fail[fail[i]];
         fail[i]++;
     }
 }

 MAT qpow(int x){
     for (;x;x=(x>>),m2=m2*m2) if (x&) m1=m1*m2;
     return m1;
 }

 int main(){
     scanf("%d%d%d",&n,&m,&p);
     scanf("%s",s+);
     kmp();
     m1.x=m;m1.y=;m1.m[][]=;
     m2.x=m2.y=m;
     for (int i=;i<=m;i++) m1.m[i][]=;
     for (int i=;i<=m;i++) for (int j=;j<=m;j++) m2.m[i][j]=;
     for (int j=;j<m;j++){
         for (int k='',now=j+;k<='';k++,now=j+){
             while (k!=s[now] && now)now=fail[now];
             m2.m[now+][j+]++;
         }
     }
     printf("%d\n",sum(qpow(n)));
     return ;
 }

正解

为什么感觉自己的kmp写的好奇怪。。