c/c++语言开发共享洛谷P3346 [ZJOI2015]诸神眷顾的幻想乡(广义后缀自动机)

题意

题目链接

sol

广义sam的板子题。

首先叶子节点不超过20，那么可以直接对每个叶子节点为根的子树插入到广义sam中。

因为所有合法的答案一定是某个叶子节点为根的树上的一条链，因此这样可以统计出所有合法的答案

然后就是经典的本质不同子串问题了，(ans = sum len[i] – len[fa[i]])

#include<bits/stdc++.h> #define ll long long  using namespace std; const int maxn = 2e6 + 10; inline int read() {     char c = getchar(); int x = 0, f = 1;     while(c < '0' || c > '9') {if(c == '-') f = -1; c = getchar();}     while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();     return x * f; } int n, c, a[maxn], deg[maxn]; namespace sam {     int fa[maxn], len[maxn], ch[maxn][11], tot = 1, root = 1, las = 1;     int insert(int x, int pre) {         int now = ++tot; len[now] = len[pre] + 1;         for(; pre && !ch[pre][x]; pre = fa[pre]) ch[pre][x] = now;         if(!pre) {fa[now] = root; return now;}         int q = ch[pre][x];         if(len[q] == len[pre] + 1) fa[now] = q;         else {             int nq = ++tot; fa[nq] = fa[q]; len[nq] = len[pre] + 1;             memcpy(ch[nq], ch[q], sizeof(ch[q]));             for(; pre && ch[pre][x] == q; pre = fa[pre]) ch[pre][x] = nq;             fa[q] = fa[now] = nq;         }         return now;     }     ll calc() {         ll ans = 0;         for(int i = 1; i <= tot; i++) ans += len[i] - len[fa[i]];         return ans;     } } vector<int> v[maxn], node; void dfs(int x, int _fa, int p) {     p = sam::insert(a[x], p);     for(auto &to : v[x]) {         if(to == _fa) continue;         dfs(to, x, p);     } }    int main() {     n = read(); c = read();     for(int i = 1; i <= n; i++) a[i] = read();     for(int i = 1; i <= n - 1; i++) {         int x = read(), y = read();         v[x].push_back(y); deg[x]++;         v[y].push_back(x); deg[y]++;     }     for(int i = 1; i <= n; i++)          if(deg[i] == 1) sam::las = 1, dfs(i, 0, 1);     cout << sam::calc();     return 0; }