Submission #885786

#	Time	Username	Problem	Language	Result	Execution time	Memory
885786		AgentPengin	Lampice (COCI19_lampice)	C++14	110 / 110	1878 ms	29276 KiB

lampice

/**
 *    author:  AgentPengin ( Độc cô cầu bại )
 *    created: 23.12.2022 10:08:02
 *    too lazy to update time
**/
#include<bits/stdc++.h>

#define EL '\n'
#define fi first
#define se second
#define NAME "TASK"
#define ll long long
#define lcm(a,b) (a/gcd(a,b))*b
#define db(val) "["#val" = " << (val) << "] "
#define bend(v) (v).begin(),(v).end()
#define sz(v) (int)(v).size()
#define ex exit(0)

using namespace std;

const ll mod = 1e9 + 7;
const int inf = 0x1FFFFFFF;
const int MAXN = 2e5 + 5;
const ll base = 35711;

int n,Len,valid[MAXN],child[MAXN],mx_depth;
char a[MAXN];
vector<int> adj[MAXN];
vector<pair<int,ll>> b;
ll po[MAXN];
unordered_map<ll,bool> f[MAXN];

void countChild(int u,int p) {
	child[u] = 1;
	for (auto v : adj[u]) {
		if (v != p && valid[v]) {
			countChild(v,u);
			child[u] += child[v];
		}
	}
}

bool dfs(int u,int p,int h,ll hashdown,ll hashup) {
	if (h > Len) return false;
	if (p) {
		hashdown = (hashdown * base + a[u]) % mod;
	}
	hashup = (hashup + 1LL * a[u] * po[h - 1]) % mod;
	ll x = (hashup * po[Len - h] - hashdown + mod) % mod;
	if (!p) f[h][x] = true;
	if (f[Len - h + 1].find(x) != f[Len - h + 1].end()) return true;
	
	for (auto v : adj[u]) {
		if (v != p && valid[v]) {
			if (!p) b.clear();
			if (dfs(v,u,h + 1,hashdown,hashup)) return true;
			if (!p) {
				for (auto x : b) {
					f[x.fi][x.se] = true;
				}
			}
		}
	}
	mx_depth = max(mx_depth,h);
	b.push_back({h,x});
	return false;
}

bool solve(int u,int n) {
	countChild(u,0);
	int flag = 1,half = n / 2;
	while(flag) {
		flag = 0;
		for (auto v : adj[u]) {
			if (valid[v] && child[v] < child[u] && child[v] > half) {
				u = v;
				flag = true;
				break;
			}
		}
	}
	countChild(u,0);
	if (dfs(u,0,1,0,0)) return true;
	for (int i = 1;i <= mx_depth;i++) f[i].clear();
	mx_depth = 0;
	valid[u] = false;
	for (auto v : adj[u]) {
		if (valid[v]) {
			if (solve(v,child[v])) return true;
		}
	}
	return false;
}

bool check(int len) {
	Len = len;
	for (int i = 1;i <= n;i++) {
		valid[i] = 1;
		f[i].clear();
	} 
	return solve(1,n);
}

signed main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    if (ifstream(NAME".inp")) {
        freopen(NAME".inp","r",stdin);
        freopen(NAME".out","w",stdout);
    }
    cin >> n;
    for (int i = 1;i <= n;i++) cin >> a[i];
    for (int i = 1;i < n;i++) {
    	int u,v; cin >> u >> v;
    	adj[u].push_back(v);
    	adj[v].push_back(u);
    }
    po[0] = 1;
    for (int i = 1;i <= n;i++) po[i] = po[i - 1] * base % mod;
    int l = 0,r = (n - 1) / 2;
    while(l < r) {
    	int mid = (l + r + 1) >> 1;
    	if (check(mid * 2 + 1)) {
    		l = mid;
    	} else {
    		r = mid - 1;
    	}
    }
    int ans = r * 2 + 1;
    l = 0,r = n / 2;
    while(l < r) {
    	int mid = (l + r + 1) >> 1;
    	if (check(mid * 2)) {
    		l = mid;
    	} else r = mid - 1;
    }
    cout << max(ans,r * 2);
    cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
    return 0;
}
// agent pengin wants to take apio (with anya-san)

Compilation message (stderr)

lampice.cpp: In function 'int main()':
lampice.cpp:107:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  107 |         freopen(NAME".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:108:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  108 |         freopen(NAME".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 25 / 25
• Subtask 3: 31 / 31
• Subtask 4: 37 / 37