hash(2018年CSUST省赛选拔赛第一场B题+hash+字典树）

题目链接：http://csustacm.com:4803/problem/1006

题目：

思路：正如题目一样，本题是一个hash，比赛的时候用的字典树，但是不知道为什么一直RE（听学长说要动态开点，但是没学字典树，瞎套的板子，可能真的是我姿势不对吧~），赛后学了一边hash（字符串题只会上星期学的kmp）后把这题补了一下。这题就最后比较时需要将每个节点的从1到该节点路径上所有的字母组成一个新的字符串，然后与题目给的n个字符串进行匹配（匹配定义题目中有说），问是否所有的字符串都至少与给的n个字符串中的一个匹配，因此我们需要借助dfs来处理新的串，我们用一个vis来标记原来那n个字符串的字串的hash值，在跑dfs时顺便判定，降低复杂度。

代码实现如下：

 #include <set>
 #include <map>
 #include <queue>
 #include <stack>
 #include <cmath>
 #include <bitset>
 #include <cstdio>
 #include <string>
 #include <vector>
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <unordered_map>
 using namespace std;

 typedef long long ll;
 typedef pair<ll, ll> pll;
 typedef pair<ll, int> pli;
 typedef pair<int, ll> pil;;
 typedef pair<int, int> pii;
 typedef unsigned long long ull;

 #define lson i<<1
 #define rson i<<1|1
 #define bug printf("*********\n");
 #define FIN freopen("D://code//in.txt", "r", stdin);
 #define debug(x) cout<<"["<<x<<"]" <<endl;
 #define IO ios::sync_with_stdio(false),cin.tie(0);

 const double eps = 1e-;
 const int mod = ;
 const int maxn = 2e5 + ;
 const double pi = acos(-);
 const int inf = 0x3f3f3f3f;
 const ll INF = 0x3f3f3f3f3f3f3f;
 const ull p = ;

 unordered_map<ull, int> vis;
 int n, m, u, v, k, x;
 int w[maxn];
 ull hs1, hs2[maxn];
 int tot;
 int head[maxn];

 struct edge {
     int v, next;
 }ed[maxn<<];

 void addedge(int u, int v) {
     ed[tot].v = v;
     ed[tot].next = head[u];
     head[u] = tot++;
     ed[tot].v = u;
     ed[tot].next = head[v];
     head[v] = tot++;
 }

 bool dfs(int u, int fa) {
     for(int i = head[u]; ~i; i = ed[i].next) {
         int v = ed[i].v;
         if(v == fa) continue;
         hs2[v] = hs2[u] * p + w[v];
         if(!vis[hs2[v]]) return false;
         if(!dfs(v, u)) return false;
     }
     return true;
 }

 int main() {
     //FIN;
     scanf("%d%d", &n, &m);
     memset(head, -, sizeof(head));
     for(int i = ; i <= n; i++) {
         scanf("%d", &k);
         hs1 = ;
         for(int j = ; j <= k; j++) {
             scanf("%d", &x);
             hs1 = hs1 * p + x;
             vis[hs1] = ;
         }
     }
     for(int i = ; i <= m; i++) {
         scanf("%d", &w[i]);
     }
     for(int i = ; i < m; i++) {
         scanf("%d%d", &u, &v);
         addedge(u, v);
     }
     if(!vis[w[]]) {
         puts("NO");
     } else {
         hs2[] = w[];
         if(dfs(, )) puts("YES");
         else puts("NO");
     }
     return ;
 }

---

补字典树写法：

 #include <set>
 #include <map>
 #include <queue>
 #include <stack>
 #include <cmath>
 #include <bitset>
 #include <cstdio>
 #include <string>
 #include <vector>
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <unordered_map>
 using namespace std;

 typedef long long ll;
 typedef pair<ll, ll> pll;
 typedef pair<ll, int> pli;
 typedef pair<int, ll> pil;;
 typedef pair<int, int> pii;
 typedef unsigned long long ull;

 #define lson i<<1
 #define rson i<<1|1
 #define bug printf("*********\n");
 #define FIN freopen("D://code//in.txt", "r", stdin);
 #define debug(x) cout<<"["<<x<<"]" <<endl;
 #define IO ios::sync_with_stdio(false),cin.tie(0);

 const double eps = 1e-;
 const int mod = ;
 const int maxn = 2e5 + ;
 const double pi = acos(-);
 const int inf = 0x3f3f3f3f;
 const ll INF = 0x3f3f3f3f3f3f3f;

 int len, root, k, m, n, x, y;
 int w[maxn];
 vector<int> v, G[maxn];

 struct Trie {
     int cnt;
     map<int, int > nxt;

     void init() {
         cnt = ;
         nxt.clear();
     }
 }T[maxn];

 void insert(int s) {
     int now = root;
     for(auto x : v[s]) {
         if(T[now].nxt[x] == ) {
             T[len].init();
             T[now].nxt[x] = len++;
         }
         now = T[now].nxt[x];
         T[now].cnt++;
     }
 }

 bool dfs(int u, int p, int now) {
     int res = ;
     for(auto v : G[u]) {
         if(v == p) continue;
         if(T[now].nxt[w[v]] == ) return ;
         res &= dfs(v, u, T[now].nxt[w[v]]);
     }
     return res;
 }

 int main() {
     FIN;
     scanf("%d%d", &n, &m);
     len = , root = ;
     T[].init();
     for(int i = ; i <= n; i++) {
         scanf("%d", &k);
         for(int j = ; j <= k; j++) {
             scanf("%d", &x);
             v[i].push_back(x);
         }
         insert(i);
     }
     for(int i = ; i <= m; i++) {
         scanf("%d", &w[i]);
     }
     for(int i = ; i < m; i++) {
         scanf("%d%d", &x, &y);
         G[x].push_back(y);
         G[y].push_back(x);
     }
     if(T[].nxt[w[]] == ) puts("NO");
     else {
         if(dfs(, , T[].nxt[w[]])) puts("YES");
         else puts("NO");
     }
     return ;
 }