洛谷P3346 [ZJOI2015]诸神眷顾的幻想乡(广义后缀自动机)

题意

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;

}