HDOJ 5469 Antonidas 树分治

#include 
using namespace std;
typedef long long LL;

#define mp(x, y) make_pair(x, y)
const int maxn = 10005;
const int maxm = 20005;
const int INF = 0x3f3f3f3f;
const int mod = 1e9+7;
const LL x = 1e6+3;

struct Edge
{
        int v;
        Edge *next;
}*H[maxn], *edges, E[maxm];

vector > dis;
bool isp[maxn];
bool iss[maxn];
int pre[maxn];
int suf[maxn];
char s[maxn];
char a[maxn];
bool done[maxn];
int size[maxn];
int mx[maxn];
LL xp[maxn];
int n, root, nsize, ans, ml;

LL powmod(LL a, LL b)
{
        LL res = 1, base = a;
        while(b) {
                if(b % 2) res = res * base % mod;
                base = base * base % mod;
                b /= 2;
        }
        return res;
}

void addedges(int u, int v)
{
        edges->v = v;
        edges->next = H[u];
        H[u] = edges++;
}

void init()
{
        edges = E;
        memset(H, 0, sizeof H);
        memset(isp, 0, sizeof isp);
        memset(iss, 0, sizeof iss);
        memset(done, 0, sizeof done);
}

void getroot(int u, int fa)
{
        mx[u] = 0, size[u] = 1;
        for(Edge *e = H[u]; e; e = e->next) if(!done[e->v] && e->v != fa) {
                int v = e->v;
                getroot(v, u);
                size[u] += size[v];
                mx[u] = max(mx[u], size[v]);
        }
        mx[u] = max(mx[u], nsize - size[u]);
        if(mx[u]  ml) return;
        dis.push_back(mp(dist, dep));
        for(Edge *e = H[u]; e; e = e->next) if(e->v != fa && !done[e->v]) {
                int v = e->v;
                getdis(v, u, dep + 1, (dist + xp[dep] * (a[v]) % mod) % mod);
        }
}

void solve(int u)
{
        if(ans) return;
        done[u] = true;
        int t = a[u];
        if(t == pre[1]) isp[1] = true;
        if(t == suf[ml]) iss[ml] = true;
        if(ml == 1 && t == pre[1]) ans = 1;
        
        for(Edge *e = H[u]; e; e = e->next) if(!done[e->v]) {
                int v = e->v;
                dis.clear();
                getdis(v, v, 1, a[v]);
                for(int i = 0; i next) if(!done[e->v]) {
                int v = e->v;
                dis.clear();
                getdis(v, v, 1, a[v] );
                for(int i = 0; i next) if(!done[e->v]) {
                int v = e->v;
                mx[0] = nsize = size[v];
                getroot(v, root = 0);
                solve(root);
        }
}

void work()
{
        int u, v;
        scanf("%d", &n);
        for(int i = 1; i = 1; i--) suf[i] = (suf[i+1] * x + s[i]) % mod;
        
        ans = 0;
        mx[0] = nsize = n;
        getroot(1, root = 0);
        solve(root);
        
        if(ans == 1) printf("Findn");
        else printf("Impossiblen");
}

int main()
{
        xp[0] = 1;
        for(int i = 1; i