UVA 11468 Substring （AC自动机）

用把失配边也加到正常边以后AC自动机，状态是长度递减的DAG，每次选一个不会匹配字符的转移。

dp[u][L]表示当前在tire树上u结点长度还剩L时候不匹配的概率，根据全概率公式跑记忆化搜索。

#include<bits/stdc++.h>
using namespace std;
typedef double ld;
const int maxnds = 21*21, sigma_size = 62;
int nds;
int ch[maxnds][sigma_size];
double p[sigma_size];
int f[maxnds];
int id[256];
bool val[maxnds];
int N;
void getF()
{
    queue<int> q;
    f[0] = 0;
    for(int c = 0; c < sigma_size; c++){
        int u = ch[0][c];
        if(u) { q.push(u); f[u] = 0; }
    }
    while(q.size()){
        int r = q.front(); q.pop();
        for(int c = 0; c < sigma_size; c++){
            int u = ch[r][c];
            if(!u) {
                ch[r][c] = ch[f[r]][c]; continue;
            }
            q.push(u);
            int v = f[r];
            while(v && !ch[v][c]) v = f[v];
            f[u] = ch[v][c];
            val[u] |= val[f[u]];
        }
    }
}

void add(char *s)
{
    int n = strlen(s), u = 0;
    for(int i = 0; i < n; i++){
        int c = id[s[i]];
        if(!ch[u][c]){
            memset(ch[nds],0,sizeof(ch[nds]));
            val[nds] = false;
            ch[u][c] = nds++;
        }
        u = ch[u][c];
    }
    val[u] = true;
}
const int maxL = 101;
ld dp[maxnds][maxL];
bool vis[maxnds][maxL];
bool exist[sigma_size];

ld dfs(int u,int L)
{
    if(!L) return 1;
    if(vis[u][L]) return dp[u][L];
    vis[u][L] = true;
    ld &ret = dp[u][L];
    ret = 0;
    for(int i = 0; i < sigma_size; i++)if(exist[i]){
        if(!val[ch[u][i]]) ret += p[i]*dfs(ch[u][i],L-1);
    }
    return ret;
}

int id_cnt;

void init()
{
    memset(ch[0],0,sizeof(ch[0]));
    nds = 1;
    val[0] = false;
    memset(exist,0,sizeof(exist));
}

#define cerid ,cout<<id[i]<<endl
#define cer(x) cout<<x<<endl;
const int maxn = 25;
char temp[maxn];
int main()
{
    //freopen("in.txt","r",stdin);
    for(int i = '0'; i <= '9'; i++) id[i] = i-'0' ;
    for(int i = 'A'; i <= 'Z'; i++) id[i] = i-'A'+10 ;
    for(int i = 'a'; i <= 'z'; i++) id[i] = i-'a'+36 ;
    int T;cin>>T;
    int kas = 0;
    while(T--){
        init();
        int K; scanf("%d",&K);
        for(int i = 0; i < K; i++){
            scanf("%s",temp);
            add(temp);
        }
        scanf("%d",&N);
        for(int i = 0; i < N; i++){
            scanf("%s",temp);
            scanf("%lf",p+id[*temp]);
            exist[id[*temp]] = true;
        }
        getF();
        int L; scanf("%d",&L);
        memset(vis,0,sizeof(vis));
        printf("Case #%d: %lf
",++kas,dfs(0,L));
    }
    return 0;
}