#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 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+10], h[2*maxm+10][maxn], dp[mask][2*maxm+10];
vector<int> t[maxn], g[maxn], G[maxm+10];
vector<pii> ver;
bool vis[maxn];
void dfs(int v, int *h, int p = -1){
for (auto u: t[v]){
if (u != p){
h[u] = h[v] + 1;
dfs(u, h, v);
}
}
}
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);
cin >> n >> S >> T;
ver.push_back({S, -1});
ver.push_back({T, -1});
for (int i = 1; i < n; i++){
int u, v, w; cin >> u >> v >> w;
t[u].push_back(v);
t[v].push_back(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;
ver.push_back({u, m});
ver.push_back({v, m});
m++;
}
}
assert(m <= 20);
sort(all(ver));
ver.resize(distance(ver.begin(), unique(all(ver))));
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]);
}
}
}
int vers = ver.size();
for (int i = 0; i < vers; i++){
dfs(ver[i].F, h[i]);
}
for (int i = 0; i < vers; i++){
dp[0][i] = h[i][T];
}
for (int msk = 1; msk < (1 << m); msk++){
for (int i = 0; i < vers; i++){
int v = ver[i].F;
dp[msk][i] = inf;
if (ver[i].F == T){
dp[msk][i] = 0;
continue;
}
for (int j = 0; j < vers; j++){
if (ver[j].S == -1 && ver[i].F == T && par[msk][comp[T]] == par[msk][comp[v]]){
dp[msk][i] = min(dp[msk][i], h[i][T]);
}
else if (ver[j].S != -1 && ((msk >> ver[j].S) & 1) && par[msk][comp[ver[j].F]] == par[msk][comp[v]]){
dp[msk][i] = min(dp[msk][i], dp[msk^(1 << ver[j].S)][j] + h[i][edge[ver[j].S][2]] + h[j][edge[ver[j].S][2]]);
}
}
}
}
for (int i = 0; i < vers; i++){
if (ver[i].F == S) return cout << (dp[(1 << m) - 1][i] == inf? -1: dp[(1 << m) - 1][i]) << '\n', 0;
}
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
24 ms |
47316 KB |
Output is correct |
| 2 |
Correct |
24 ms |
47348 KB |
Output is correct |
| 3 |
Incorrect |
218 ms |
60956 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
26 ms |
47444 KB |
Output is correct |
| 2 |
Correct |
27 ms |
47324 KB |
Output is correct |
| 3 |
Incorrect |
26 ms |
47832 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
24 ms |
47316 KB |
Output is correct |
| 2 |
Correct |
24 ms |
47348 KB |
Output is correct |
| 3 |
Incorrect |
218 ms |
60956 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
