Submission #635636

#	Time	Username	Problem	Language	Result	Execution time	Memory
635636		NothingXD	LOSTIKS (INOI20_lostiks)	C++17	100 / 100	1949 ms	315624 KiB

Main

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//typedef __uint128_t L;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
	cerr << " " << H;
	debug_out(T...);
}

#define debug(...) cerr << "(" << #__VA_ARGS__ << "):", debug_out(__VA_ARGS__)
#define all(x) x.begin(), x.end()
#define MP(x, y) make_pair(x, y)
#define F first
#define S second

const int maxn = 1e6 + 10;
const int lg = 20;
const int maxm = 20;
const int mask = (1 << 20);
const int inf = 1e9;

int n, m, S, T, edge[maxm][3], comp[maxn], cnt, sz, par[mask][maxm+1], dis[maxm+1][maxm+1], h[maxn], pare[maxn][lg], dp[mask][maxm+1];
vector<int> g[maxn], G[maxm+1];
bool vis[maxn];

int first[maxn], to[maxn << 1], nxt[maxn << 1], ecnt;

void add(int u, int v){
	nxt[++ecnt] = first[u];
	to[ecnt] = v;
	first[u] = ecnt;
}

void dfs(int v,int p = -1){
	pare[v][0] = p;
	for (int i = 1; i < lg; i++) if (pare[v][i-1] != -1) pare[v][i] = pare[pare[v][i-1]][i-1];
	for (int i = first[v]; i; i = nxt[i]){
		int u = to[i];
		if (u != p){
			h[u] = h[v] + 1;
			dfs(u, v);
		}
	}
}

int getpar(int v, int x){
	for (int i = 0; i < lg; i++){
		if ((x >> i) & 1) v = pare[v][i];
	}
	return v;
}

int lca(int u, int v){
	if (h[u] < h[v]) swap(u, v);
	u = getpar(u, h[u] - h[v]);
	if (u == v) return u;
	for(int i = lg - 1; ~i; i--){
		if (pare[v][i] != pare[u][i]){
			v = pare[v][i];
			u = pare[u][i];
		}
	}
	return pare[u][0];
}

void getcomp(int v, int p = -1){
	vis[v] = true;
	comp[v] = cnt;
	for (auto u: g[v]) if (u != p) getcomp(u, v);
}

void getpar(int v, int *par, int p = -1){
	vis[v] = true;
	par[v] = sz;
	for (auto u : G[v]) if (u != p) getpar(u, par, v);
}

int main(){
	//ios_base::sync_with_stdio(false); cin.tie(0);
	
	memset(pare, -1, sizeof pare);

	scanf("%d%d%d", &n, &S, &T);
	for (int i = 1; i < n; i++){
		int u, v, w; scanf("%d%d%d", &u, &v, &w);
		add(u, v);
		add(v, u);
		if (w == 0){
			g[u].push_back(v);
			g[v].push_back(u);
		}
		else{
			edge[m][0] = u;
			edge[m][1] = v;
			edge[m][2] = w;
			m++;
		}
	}

	dfs(S);

	for (int i = 0; i < m; i++){
		if (h[edge[i][0]] > h[edge[i][1]]) swap(edge[i][0], edge[i][1]);
	}

	for (int i = 0; i <= m; i++){
		for (int j = 0; j <= m; j++){
			int v = (i == m? S: edge[i][0]);
			int u = (j == m? T: edge[j][0]);
			if (j != m){
				dis[i][j] = h[v] + h[u] + 2 * h[edge[j][2]] - 2 * h[lca(v, edge[j][2])] - 2 * h[lca(u, edge[j][2])];
			}
			else{
				dis[i][j] = h[v] + h[u] - 2 * h[lca(u, v)];
			}
		}
	}

	for (int i = 1; i <= n; i++){
		if (!vis[i]){
			getcomp(i);
			cnt++;
		}
	}

	for (int i = 0; i < (1 << m); i++){
		for (int j = 0; j < m+1; j++){
			G[j].clear();
			vis[j] = false;
		}
		for (int j = 0; j < m; j++){
			if (!((i >> j) & 1)){
				G[comp[edge[j][0]]].push_back(comp[edge[j][1]]);
				G[comp[edge[j][1]]].push_back(comp[edge[j][0]]);
			}
		}
		sz = 0;
		for (int j = 0; j < m+1; j++){
			if (!vis[j]){
				sz++;
				getpar(j, par[i]);
			}
		}
	}

	for (int i = 0; i <= m; i++){
		dp[0][i] = dis[i][m];
	}

	for (int msk = 1; msk < (1 << m); msk++){
		for (int i = 0; i <= m; i++){
			int v = (i == m? S: edge[i][0]);
			dp[msk][i] = inf;
			if (par[msk][comp[T]] == par[msk][comp[v]]){
				dp[msk][i] = dis[i][m];
				continue;
			}
			for (int tmp = msk; tmp; tmp ^= tmp & -tmp){
				int j = __builtin_ctz(tmp);
				if (par[msk][comp[edge[j][2]]] == par[msk][comp[v]] && par[msk][comp[edge[j][0]]] == par[msk][comp[v]]){
					dp[msk][i] = min(dp[msk][i], dp[msk^(1 << j)][j] + dis[i][j]);
				}
			}
		}
	}

	printf("%d\n", (dp[(1 << m) - 1][m] == inf? -1: dp[(1 << m) - 1][m]));



	return 0;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:92:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |  scanf("%d%d%d", &n, &S, &T);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~
Main.cpp:94:21: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   94 |   int u, v, w; scanf("%d%d%d", &u, &v, &w);
      |                ~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 23 / 23
• Subtask 2: 36 / 36
• Subtask 3: 41 / 41