제출 #159905

#제출 시각아이디문제언어결과실행 시간메모리
159905XCoderCommuter Pass (JOI18_commuter_pass)C++14
0 / 100
2077 ms21008 KiB
#include <bits/stdc++.h> #define FOR(i,s,e) for(int i=(s);i<(int)(e);i++) #define FOE(i,s,e) for(int i=(s);i<=(int)(e);i++) #define REP(i,n) FOR(i,0,n) #define ALL(x) (x).begin(), (x).end() #define CLR(s) memset(s,0,sizeof(s)) #define PB push_back #define ITER(v) __typeof((v).begin()) #define FOREACH(i,v) for(ITER(v) i=(v).begin();i!=(v).end();i++) #define x first #define y second using namespace std; typedef long long LL; typedef pair<int,int> pii; typedef pair<LL, LL> pll; typedef map<int,int> mii; typedef vector<int> vi; const LL INF = 1LL << 40; using Graph = vector<vector<pii>>; using Dist = vector<LL>; using Node = tuple<LL, int>; // <cost, node_id> int N, M, S, T, U, V; Graph G; Dist compute_shortest_path(Graph &G, vector<int> src_nodes, int N) { Dist D(N + 1, INF); priority_queue<Node, vector<Node>, greater<Node>> pq; for (auto &src : src_nodes) { D[src] = 0LL; pq.push({D[src], src}); } while (!pq.empty()) { LL cur; int x; tie(cur, x) = pq.top(); pq.pop(); if (D[x] > cur) continue; for (auto &it : G[x]) { LL cost; int y; tie(y, cost) = it; if (cur + cost < D[y]) { D[y] = cur + cost; pq.push({D[y], y}); } } } return D; } Dist S_dist, T_dist, U_dist, V_dist; LL ST_shortest_path_cost; void dfs(Graph &G, Dist &U_dist, Dist &V_dist, int x, LL u_min_dist, LL &ans) { // u -> some nodes visited -> x -> v u_min_dist = min(u_min_dist, U_dist[x]); ans = min(ans, u_min_dist + V_dist[x]); // x : current node // DFS - traverse all possible shortest paths for (auto &edge : G[x]) { int y, cost; tie(y, cost) = edge; if (S_dist[x] + T_dist[y] + cost == ST_shortest_path_cost) { // S -> x -> y -> T is a possible S-T shortest path dfs(G, U_dist, V_dist, y, u_min_dist, ans); } } } int main() { int A, B, C; cin >> N >> M >> S >> T >> U >> V; G.resize(N + 1); FOR(_, 0, M) { cin >> A >> B >> C; G[A].PB({B, C}); G[B].PB({A, C}); } S_dist = compute_shortest_path(G, {S}, N); T_dist = compute_shortest_path(G, {T}, N); U_dist = compute_shortest_path(G, {U}, N); V_dist = compute_shortest_path(G, {V}, N); //cout << src_dist[T] << " " << dst_dist[S] << endl; ST_shortest_path_cost = S_dist[T]; assert (S_dist[T] == T_dist[S]); // Case 1: Travel U -> some nodes along a shortest path -> V LL ans = INF; dfs(G, U_dist, V_dist, S, INF, ans); dfs(G, V_dist, U_dist, S, INF, ans); //cout << ans << endl; // Case 2: Travel U -> V via direct shortest path Dist direct_dist = compute_shortest_path(G, {U}, N); ans = min(ans, direct_dist[V]); cout << ans << endl; return 0; }
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