제출 #896093

#제출 시각아이디문제언어결과실행 시간메모리
896093starchan경주 (Race) (IOI11_race)C++17
0 / 100
3 ms18780 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)1e17 #define MX (int)2e5+5 #define fast() ios_base::sync_with_stdio(false); cin.tie(NULL) int n, k; vector<in> adj[MX]; int sz[MX]; vector<bool> cut; void dfs1(int u, int p) { sz[u] = 1; for(in vw: adj[u]) { int v = vw.f; if(cut[v]) continue; if(v == p) continue; dfs1(v, u); sz[u]+=sz[v]; } return; } vector<in> comp[MX]; vector<int> centr[MX]; int centroid(int root, int u, int p) { for(in vw: adj[u]) { int v = vw.f; if(cut[v]) continue; if(v==p) continue; if(2*sz[v] > sz[root]) return centroid(root, v, u); } return u; } void dfs2(int root, int u, int p, int lvl, int d) { comp[root].pb({d, lvl}); for(in vw: adj[u]) { int v = vw.f; int w = vw.s; if(cut[v]) continue; if(v==p) continue; int cost = d+w; if(cost > k) cost = k+1; dfs2(root, v, u, lvl+1, cost); } return; } int centroid_decomposition(int u) { dfs1(u, -1); int root = centroid(u, u, -1); cut[root] = 1; for(in vw: adj[root]) { int v = vw.f; if(cut[v]) continue; dfs2(v, v, root, 1, vw.s); centr[root].pb(centroid_decomposition(v)); } return root; } int dfs3(int u, int p) { int ans = n+1; map<int, int> freq; freq[0] = 0; for(int v: centr[u]) { ans = min(ans, dfs3(v, u)); for(in L_edge: comp[v]) { int L = L_edge.f; int dep = L_edge.s; if(L > k) continue; if(freq.find(k-L) == freq.end()) continue; ans = min(ans, dep+freq[k-L]); } for(in L_edge: comp[v]) { int L = L_edge.f; int dep = L_edge.s; if(freq.find(L) == freq.end()) freq[L] = dep; else freq[L] = min(freq[L], dep); } } return ans; } int best_path(int N, int K, int h[][2], int L[]) { n = N; k = K; for(int i = 1; i <= n; i++) adj[i].clear(); 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}); } cut.assign(n+1, 0); int root = centroid_decomposition(1); int ans = dfs3(root, -1); if(ans == (n+1)) 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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