UVA 11468【AC自动机+DP】

dp[i][j]表示走了i步走到j结点的概率。初始值dp[0][0] = 1.当走到的结点不是单词尾结点时，才能走过去。

!end[i]&&last[i] == root时，该结点才可行。

 丢掉last数组, end[i] |= end[ fail[i] ]即可。 表示i节点是某些禁止字符串的后缀。

#include <bits/stdc++.h>
using namespace std;
const int N  = 505;
int id(char c){
    if(c >= '0'&&c <= '9') return c-'0';
    if(c >= 'a'&&c <= 'z') return c-'a'+10;
    if(c >= 'A'&&c <= 'Z') return c-'A'+36;
    return -1;
}
struct Tire{
    int nex[N][62], fail[N], end[N];
    int root, L;
    int newnode(){
        memset(nex[L], -1, sizeof(nex[L]));
        end[L] = 0;
        return L++;
    }
    void init(){
        L = 0;
        root = newnode();
    }
    void insert(char* s){
        int now = root;
        for(int i = 0; s[i]; i++){
            int p = id(s[i]);
            if(nex[now][p] == -1)
                nex[now][p] = newnode();
            now = nex[now][p];
        }
        end[now] = 1;
    }
    void build(){
        queue<int> Q;
        fail[root] = root;
        for(int i = 0; i < 62; i++){
            int& u = nex[root][i];
            if(u == -1)
                u = root;
            else{
                fail[u] = root;
                Q.push(u);
            }
        }
        while(!Q.empty()){
            int now = Q.front();
            Q.pop();
            for(int i = 0; i < 62; i++){
                int& u = nex[now][i];
                if(u == -1)
                    u = nex[ fail[now] ][i];
                else{
                    fail[u] = nex[ fail[now] ][i];
                    end[u] |= end[ fail[u] ];
                    //last[u] = end[ fail[u] ]? fail[u] : last[ fail[u] ];
                    Q.push(u);
                }
            }
        }
    }
};
Tire ac;
double por[70];
char s[50];
double dp[105][N];
int main(){
    int n, k, t, ca = 1; scanf("%d", &t);
    while(t--){
        ac.init();
        scanf("%d", &k);
        for(int i = 0; i < k; i++){
            scanf("%s", s);
            ac.insert(s);
        }
        ac.build();
        memset(por, 0, sizeof(por));
        scanf("%d", &n);
        char ch;
        for(int i = 0; i < n; i++){
            scanf(" %c", &ch);
            int p = id(ch);
            scanf("%lf", por+p);
        }
        int l; scanf("%d", &l);
        memset(dp, 0, sizeof(dp));
        dp[0][0] = 1;
        for(int i = 0; i < l; i++){
            for(int j = 0; j < ac.L; j++)
                if(dp[i][j] > 0) for(int k = 0; k < 62; k++){
                    int ret = ac.nex[j][k];
                    if(!ac.end[ret])
                        dp[i+1][ret] += dp[i][j]*por[k];
                }
        }
        double ans = 0;
        for(int i = 0; i < ac.L; i++)
            ans += dp[l][i];
        printf("Case #%d: %f
", ca++, ans);
    }
    return 0;
}