【LOJ】#2072. 「JSOI2016」独特的树叶

题解

干脆题解套题解好了

毕竟我的hash方法是抄小迪的

https://www.cnblogs.com/RabbitHu/p/9165770.html

小迪太巨了%%%

之前模数是八位的WA了几个点，换成9位模数就都过了

代码

#include <bits/stdc++.h>
//#define ivorysi
#define enter putchar('\n')
#define space putchar(' ')
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define eps 1e-8
#define ba 11
#define mo 999999137
#define MAXN 100005
#define pii pair<int,int>
using namespace std;
typedef long long int64;
typedef double db;
template<class T>
void read(T &res) {
    res = 0;char c = getchar();T f = 1;
    while(c < '0' || c > '9') {
	if(c == '-') f = -1;
	c = getchar();
    }
    while(c >= '0' && c <= '9') {
	res = res * 10 + c - '0';
	c = getchar();
    }
    res *= f;
}
template<class T>
void out(T x) {
    if(x < 0) {putchar('-');x = -x;}
    if(x >= 10) {
	out(x / 10);
    }
    putchar('0' + x % 10);
}
struct node {
    int to,next;
}E[MAXN * 2];
int sumE,head[MAXN],N,fa[MAXN],siz[MAXN],D[MAXN],ans = 1000000000;
int64 F[MAXN],B[MAXN + 10];
set<int64> S;
vector<int64> son[MAXN],pre[MAXN],suf[MAXN];
bool isB;
void add(int u,int v) {
    E[++sumE].to = v;
    E[sumE].next = head[u];
    head[u] = sumE;
}
void dfs1(int u) {
    siz[u] = 1;
    son[u].clear();
    son[u].pb(0);
    for(int i = head[u] ; i ; i = E[i].next) {
	int v = E[i].to;
	if(v != fa[u]) {
	    fa[v] = u;
	    dfs1(v);
	    siz[u] += siz[v];
	    son[u].pb(F[v]);
	}
    }
    F[u] = 0;
    if(siz[u] == 1) {F[u] = 1;return;}
    sort(son[u].begin(),son[u].end());
    int s = son[u].size();
    for(int i = 1 ; i < s ; ++i) {
	F[u] =  (F[u] + B[i] * son[u][i]) % mo;
    }
    F[u] = F[u] * siz[u] % mo;

}
void dfs2(int u,int64 Fa) {

    if(fa[u]) son[u].pb(Fa);
    sort(son[u].begin(),son[u].end());
    int s = son[u].size();
    pre[u].clear();suf[u].clear();
    pre[u].resize(s);
    suf[u].resize(s + 1);
    pre[u][0] = 0;suf[u][s] = 0;
    for(int i = 1 ; i < s ; ++i) {
	pre[u][i] = (pre[u][i - 1] + B[i] * son[u][i]) % mo;
    }
    for(int i = s - 1 ; i >= 1 ; --i) {
	suf[u][i] = (suf[u][i + 1] + B[i - 1] * son[u][i]) % mo;
    }
    if(!isB) S.insert(pre[u][s - 1] * siz[1] % mo);
    if(isB && D[u] == 1) {
	if(!fa[u]) {
	    if(S.find(son[u][1]) != S.end()) {ans = min(ans,u);}
	}
	else if(S.find(Fa) != S.end()) {ans = min(ans,u);}
    }
    for(int i = head[u] ; i ; i = E[i].next) {
	int v = E[i].to;
	if(v != fa[u]) {
	    int t = lower_bound(son[u].begin(),son[u].end(),F[v]) - son[u].begin();
	    int64 T = (pre[u][t - 1] + suf[u][t + 1]) % mo;
	    T = T * (siz[1] - siz[v]) % mo;
	    if(siz[1] - siz[v] == 1) T = 1;
	    dfs2(v,T);
	}
    }
}
void Solve() {
    read(N);
    B[0] = 1;
    for(int i = 1 ; i <= N + 3 ; ++i) B[i] = B[i - 1] * ba % mo;
    int u,v;
    for(int i = 1 ; i < N ; ++i) {
	read(u);read(v);
	add(u,v);add(v,u);
    }
    dfs1(1);
    dfs2(1,0);
    memset(head,0,sizeof(head));
    memset(fa,0,sizeof(fa));
    memset(siz,0,sizeof(siz));
    sumE = 0;
    for(int i = 1 ; i <= N ; ++i) {
	read(u);read(v);
	add(u,v);add(v,u);
	D[u]++;D[v]++;
    }
    isB = 1;
    dfs1(1);
    dfs2(1,0);
    out(ans);enter;
}
int main() {
#ifdef ivorysi
    freopen("f1.in","r",stdin);
#endif
    Solve();
    return 0;
}