#include <bits/stdc++.h>
//#pragma GCC optimize ("Ofast,unroll-loops")
#pragma GCC target ("avx2")
using namespace std;
typedef long long ll;
typedef pair<int, int> pp;
#define rep(i,l,r) for(int i = (l); i < (r); i++)
#define per(i,r,l) for(int i = (r); i >= (l); i--)
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
#define pb push_back
#define ff first
#define ss second
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void IOS(){
cin.tie(0) -> sync_with_stdio(0);
// #ifndef ONLINE_JUDGE
// freopen("inp.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
// #endif
}
const ll mod = 1e9 + 7, maxn = 1e6 + 5, maxm = 20, lg = 20, inf = ll(1e9) + 5;
int val[maxn], ed[maxm], nxt[maxm], tmp, n;
vector<pp> adj[maxn];
int dq[maxn], st, en, tmp_vl[maxm][maxm];
int par[maxn][lg], h[maxn];
void dfs(int r){
dq[st = 0] = r, en = 1;
while(st < en){
int r = dq[st++];
rep(i,1,lg) par[r][i] = par[par[r][i-1]][i-1];
for(auto&[c, w]: adj[r]) if(c - par[r][0]){
val[c] = val[r];
h[c] = h[r] + 1;
par[c][0] = r;
if(w + 1){
ed[tmp] = r;
nxt[tmp] = w;
val[c] |= 1<<tmp;
tmp++;
}
dq[en++] = c;
}
}
// val[r] |= val[p];
// for(auto&[c, w]: adj[r]) if(c - p){
// if(w + 1){
// ed[tmp] = r;
// nxt[tmp] = w;
// val[c] = 1<<tmp;
// tmp++;
// dfs(c, r);
// } else{
// dfs(c, r);
// }
// }
}
//void dfs2(int r, int id){
//// vector<pp> stk;
//// for(auto&[c, w]: adj[r]) if(c - p){
//// dist[id][c] = dist[id][r] + 1;
//// dfs2(c, r);
//// }
// dq[st = 0] = r, en = 1;
// fill(dist[id], dist[id] + n, -1);
// dist[id][r] = 0;
// while(st < en){
// int r = dq[st++];
// for(auto&[c, w]: adj[r]) if(dist[id][c] == -1){
// dist[id][c] = dist[id][r] + 1;
// dq[en++] = c;
// }
// }
//}
int lca(int u, int v){
if(h[u] > h[v]) swap(u, v);
per(i,lg-1,0) if(h[par[v][i]] >= h[u]) v = par[v][i];
if(u == v) return u;
per(i,lg-1,0) if(par[u][i] - par[v][i]) u = par[u][i], v = par[v][i];
return par[u][0];
}
int dist(int u, int v){
return h[u] + h[v] - (h[lca(u, v)]<<1);
}
int dp[maxm][1<<maxm];
int main(){ IOS();
// tof to zatet ba in limitaie soal
int s, t; cin >> n >> s >> t; s--, t--;
int m = 0;
rep(i,1,n){
int u, v, w; cin >> u >> v >> w; u--, v--, w--;
adj[u].pb({v, w});
adj[v].pb({u, w});
m += w != -1;
}
dfs(s);
// rep(i,0,m){
// dfs2(ed[i], i);
// }
// dfs2(s, m);
rep(i,0,m){
rep(j,0,m){
tmp_vl[i][j] = dist(ed[i], nxt[j]) + dist(ed[j], nxt[j]);
}
}
auto chk = [&](int msk, int r){
return (val[r]&msk) == val[r];
};
vector<int> is(m), nis(m);
int ptr_is = 0, ptr_nis = 0;
per(i,(1<<m)-1,1){
ptr_is = ptr_nis = 0;
rep(e,0,m) {
if(i>>e&1){
if(chk(i, ed[e])) is[ptr_is++] = e;
}else{
if(chk(i, nxt[e]) && chk(i, ed[e])) nis[ptr_nis++] = e;
}
}
rep(x,0,ptr_is){
int e = is[x];
dp[e][i] = inf;
if(chk(i, t)){
dp[e][i] = dist(ed[e], t);
}else{
rep(j,0,ptr_nis){
dp[e][i] = min(dp[e][i], dp[nis[j]][i^(1<<nis[j])] + tmp_vl[e][nis[j]]);
}
}
}
}
int ans = inf;
rep(i,0,m){
if(chk(0, nxt[i]) && chk(0, ed[i])) ans = min(ans, dp[i][1<<i] + dist(s, nxt[i]) + dist(ed[i], nxt[i]));
}
if(chk(0, t)){
ans = dist(s, t);
}
cout << (ans == inf? -1: ans) << '\n';
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
12 ms |
23764 KB |
Output is correct |
| 2 |
Correct |
12 ms |
23800 KB |
Output is correct |
| 3 |
Incorrect |
69 ms |
36524 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
12 ms |
23740 KB |
Output is correct |
| 2 |
Correct |
13 ms |
23756 KB |
Output is correct |
| 3 |
Incorrect |
12 ms |
23892 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
12 ms |
23764 KB |
Output is correct |
| 2 |
Correct |
12 ms |
23800 KB |
Output is correct |
| 3 |
Incorrect |
69 ms |
36524 KB |
Output isn't correct |
| 4 |
Halted |
0 ms |
0 KB |
- |
