Submission #896128

#TimeUsernameProblemLanguageResultExecution timeMemory
896128starchanRace (IOI11_race)C++17
0 / 100
3059 ms13656 KiB
#include "race.h" #include<bits/stdc++.h> using namespace std; #define in pair<int, int> #define f first #define s second #define pb push_back #define pob pop_back #define INF (int)1e9 #define MX (int)2e5+5 #define LMX (int)1e6+5 #define fast() ios_base::sync_with_stdio(false); cin.tie(NULL) int n, k; vector<in> adj[MX]; int sz[MX]; bool cut[MX]; void calc_subtree(int u, int p) { sz[u] = 1; for(auto [v, w]: adj[u]) { if(v==p) continue; if(cut[v]) continue; calc_subtree(v, u); sz[u]+=sz[v]; } return; } int centroid(int root, int u, int p) { for(auto [v, w]: adj[u]) { if(cut[v]) continue; if(v==p) continue; if(2*sz[v] > sz[root]) return centroid(root, v, u); } return u; } vector<int> curr; vector<int> on; vector<int> best(LMX, INF); int ans = INF; void ritul(int u, int p, int lvl, int dist) { if(dist > k) return; ans = min(ans, lvl+best[k-dist]); for(auto [v, w]: adj[u]) { if((dist+w) > k) continue; ritul(v, u, lvl+1, dist+w); } return; } void ritul2(int u, int p, int lvl, int dist) { if(dist > k) return; curr.pb(dist); best[dist] = min(best[dist], lvl); for(auto [v, w]: adj[u]) { if((dist+w) > k) continue; ritul2(v, u, lvl+1, dist+w); } return; } void centroid_decomp(int u) { calc_subtree(u, -1); int root = centroid(u, u, -1); cut[root] = 1; curr.clear(); for(auto [v, w]: adj[root]) { if(cut[v]) continue; ritul(v, root, 1, w); ritul2(v, root, 1, w); } for(int t: curr) best[t] = INF; for(auto [v, w]: adj[root]) { if(cut[v]) continue; centroid_decomp(v); } return; } int best_path(int N, int K, int h[][2], int L[]) { n = N; k = K; for(int i = 0; i < n-1; i++) { int u = h[i][0]; int v = h[i][1]; u++; v++; int l = L[i]; adj[u].pb({v, l}); adj[v].pb({u, l}); } centroid_decomp(1); if(ans == INF) ans = -1; return ans; } /* signed main() { int V, KK; cin >> V >> KK; int h[V-1][2]; int L[V-1]; for(int i = 0; i < V-1; i++) cin >> h[i][0] >> h[i][1] >> L[i]; int ok = best_path(V, KK, h, L); cout << ok << endl; return 0; } */
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