EOJ Monthly 2019.11 B字母游戏

#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 1005
const int mod[2]={19260817,19190504},mul[2]={29,11};
int hash[2][maxn],ha[2][maxn][10][10],flag[10];
int q[5][10],top[5],n,m,K,ans,a[10],tail,now[2];
char s[maxn];
using namespace std;
struct in
{
    int q[2];     
}b[maxn];
bool cmp(in x,in y)
{
    if (x.q[0]==y.q[0]) return x.q[1]<y.q[1];
    return x.q[0]<y.q[0];
}
void dfs(int x,int last)
{
    int i;
    if (x>tail)
    {
        int j,k,t,tot,now=0,cnt;
        for (i=0;i<last;i++)
        {
            if (top[i]==1) return;
            if (top[i]>1) now+=top[i]-1; 
        }
        if (now>K) return;    
        //printf("%d \n",now);
        for (i=1;i<=n;i++)
            for (t=0;t<=1;t++) b[i].q[t]=hash[t][i];
        for (i=0;i<last;i++) 
            for (k=2;k<=top[i];k++)
                for (j=1;j<=n;j++) 
                    for (t=0;t<=1;t++) b[j].q[t]=(b[j].q[t]-ha[t][j][q[i][k]][q[i][k]]+ha[t][j][q[i][k]][q[i][1]]+mod[t])%mod[t];        
        cnt=0;tot=1;
        sort(b+1,b+n+1,cmp);
        for (j=2;j<=n;j++)
            if (b[j].q[0]==b[j-1].q[0] && b[j].q[1]==b[j-1].q[1]) tot++;
            else 
            {
                cnt+=tot*(tot-1)/2;
                tot=1;
            }
        cnt+=tot*(tot-1)/2;
        //printf("%d %d %d\n",cnt,tot,x);
        if (cnt>ans) ans=cnt;    
        return;
    }
    for (i=0;i<last;i++)
    {
        q[i][++top[i]]=a[x];
        dfs(x+1,last);
        top[i]--;
    }
    if (last<4)
    {
        q[last][++top[last]]=a[x];
        dfs(x+1,last+1);
        top[last]--;
    }
    dfs(x+1,last);
    return;
}
int main()
{
    int now[2],i,j,k,t;
    scanf("%d%d%d",&n,&m,&K);
    for (i=1;i<=n;i++)
    {
        scanf("%s",s);
        now[0]=1;now[1]=1;
        for (j=0;j<m;j++)
        for (t=0;t<=1;t++)
        {
            for (k=0;k<8;k++) 
                ha[t][i][s[j]-‘a‘][k]=(ha[t][i][s[j]-‘a‘][k]+(‘a‘+k)*now[t]%mod[t])%mod[t];
            hash[t][i]=(hash[t][i]+s[j]*now[t]%mod[t])%mod[t];
            now[t]=now[t]*mul[t]%mod[t];
            flag[s[j]-‘a‘]=1;
        }
    }
    for (i=0;i<8;i++)
        if (flag[i]) a[++tail]=i;
    if (K>=tail-1)
    {
        printf("%d",n*(n-1)/2);
        return 0;
    }
    dfs(1,0);
    printf("%d",ans);
    return 0;
}