Submission #635727

#TimeUsernameProblemLanguageResultExecution timeMemory
635727MohammadAghilLOSTIKS (INOI20_lostiks)C++17
59 / 100
2071 ms123540 KiB
#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 void dbg(){ cerr << endl; } template<typename Head, typename... Tail> void dbg(Head h, Tail... t){ cerr << " " << h << ","; dbg(t...); } #define er(...) cerr << __LINE__ << " <" << #__VA_ARGS__ << ">:", dbg(__VA_ARGS__) 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, inf = ll(1e9) + 5; int val[maxn], ed[maxm], nxt[maxm], tmp, n; vector<pp> adj[maxn]; void dfs(int r, int p){ 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); } } } int dist[maxm + 1][maxn], dq[maxn], st, en; 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 dp[1<<maxm][maxm]; int main(){ IOS(); 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, -1); rep(i,0,m){ dfs2(ed[i], i); } dfs2(s, m); 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[i][e] = inf; if(chk(i, t)){ dp[i][e] = dist[e][t]; }else{ rep(j,0,ptr_nis){ int x = nis[j]; dp[i][e] = min(dp[i][e], dp[i^(1<<x)][x] + dist[e][nxt[x]] + dist[x][nxt[x]]); } } } } int ans = inf; rep(i,0,m){ if(chk(0, nxt[i]) && chk(0, ed[i])) ans = min(ans, dp[1<<i][i] + dist[m][nxt[i]] + dist[i][nxt[i]]); } if(chk(0, t)){ ans = dist[m][t]; } cout << (ans == inf? -1: ans) << '\n'; return 0; }
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