ac自动机——[TJOI2013]单词

题解：

建fail树之后，从下往上跑fail指针并且计数。答案就是每个节点的计数。

#include <bits/stdc++.h>
//#define int long long
using namespace std;
typedef long long ll;
const int N=1e6+10;
const int M=1e5+10;
const int mod=1e9+7;
vector<int> g;
vector<int> id;
int head[N],e[N],ne[N],idx,res[N];
void add(int a,int b)
{
    e[++idx]=b,ne[idx]=head[a],head[a]=idx;
}
struct Trie{
    int next[N][26], fail[N], end[N];
    int dep[N], dp[N][22];
    int root, L;
    int newnode(){
        for (int i = 0; i < 26; i++){
            next[L][i] = -1;
        }
        end[L++] = 0;
        return L - 1;
    }
    void init(){
        L = 0;
        root = newnode();
    }
    void insert(char buf[]){
        int len = (int)strlen(buf);
        int now = root;
        for (int i = 0; i < len; i++){
            if (next[now][buf[i] - 'a'] == -1){
                next[now][buf[i] - 'a'] = newnode();
            }
            now = next[now][buf[i] - 'a'];
            res[now]++;
        }
        id.push_back(now);
        end[now]++;
    }
    void build(){
        queue<int>Q;
        fail[root] = root;
        for (int i = 0; i < 26; i++){
            if (next[root][i] == -1){
                next[root][i] = root;
            }
            else{
                fail[next[root][i]] = root;
                Q.push(next[root][i]);
            }
        }
        while (!Q.empty()){
            int now = Q.front();
            Q.pop();
            g.push_back(now);
            for (int i = 0;i < 26;i++){
                if (next[now][i] == -1){
                    next[now][i] = next[fail[now]][i];
                }
                else{
                    fail[next[now][i]]=next[fail[now]][i];
                    Q.push(next[now][i]);
                }
            }
        }
    }
    void build_lca(){
        for(int i = 0 ; i < L ; i ++) add(fail[i],i);
    }
    void dfs(int u, int fa){
        dep[u] = dep[fa] + 1; dp[u][0] = fa;
        for(int i = 1 ; i <= 20 ; i ++) dp[u][i] = dp[dp[u][i - 1]][i - 1];
        for(int i=head[u];i;i=ne[i]){
            int v=e[i];
            if(v == fa) continue;
            dfs(v, u);
        }
    }
    int lca(int x, int y){
        if(dep[x] < dep[y]) swap(x, y);
        for(int i = 20; i >= 0 ; i --){
            if(dep[dp[x][i]] >= dep[y]){
                x = dp[x][i];
            }
        }
        if(x == y) return x;
        for(int i = 20 ; i >= 0 ; i --){
            if(dp[x][i] != dp[y][i]){
                x = dp[x][i], y = dp[y][i];
            }
        }
        return dp[x][0];
    }
    void debug(){
        for (int i = 0; i < L; i++){
            printf("id = %3d,fail = %3d,end = %3d,chi = [", i, fail[i], end[i]);
            for (int j = 0; j < 26; j++){
                printf("%2d", next[i][j]);
            }
            printf("]\n");
        }
    }
    void query(){
        for(int i=g.size()-1;i>=0;i--){
            res[fail[g[i]]]+=res[g[i]];
        }
    }
};
char buf[N];
Trie ac;
void solve()
{
    int n;
    scanf("%d",&n);
    ac.init();
    for(int i=1;i<=n;i++){
        scanf("%s",&buf);
        ac.insert(buf);
    }
    ac.build();
    ac.query();
    for(int i=0;i<n;i++){
        printf("%d\n",res[id[i]]);
    }
}
signed main(){
    solve();
#ifndef ONLINE_JUDGE
    cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
#endif
    return 0;
}