Submission #486779

#	Time	Username	Problem	Language	Result	Execution time	Memory
486779		socho	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	535 ms	25520 KiB

commuter_pass

/*
	Going for full
*/
#include <bits/stdc++.h>
using namespace std;
void fast() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
}
void ran() {
	srand(chrono::steady_clock::now().time_since_epoch().count());
}
long long get_rand() {
	long long a = rand();
	long long b = rand();
	return a * (RAND_MAX + 1ll) + b;
}
void usaco() {
	freopen("problem.in", "r", stdin); 
	freopen("problem.out", "w", stdout);
}
template<typename T>
using min_pq = priority_queue<T, vector<T>, greater<T>>;
#define endl '\n'
// #define double long double
#define int long long
// const int MOD = 1000 * 1000 * 1000 + 7;
// const int MOD = 998244353;
// #define cerr if(0) cerr
#define debug(x) cerr << #x << ": " << x << endl;

int n, m;
int s, t, u, v;
const int MXN = 100005;
vector<pair<int, int>> adj[MXN];
 
int distu[MXN], distv[MXN];
int dists[MXN], distt[MXN];
int dist[MXN];
bool access[MXN];
 
int result;
 
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> proc;
 
void src(int no) {
	
	for (int i=1; i<=n; i++) {
		dist[i] = LLONG_MAX;
	}
	
	proc.push({0, no});
	
	while (!proc.empty()) {
		
		pair<int, int> tr = proc.top();
		proc.pop();
		int di = tr.first, no = tr.second;
		if (dist[no] < di) continue;
		dist[no] = di;
		
		for (auto x: adj[no]) {
			int ot = x.first;
			int od = x.second + di;
			if (dist[ot] > od) {
				dist[ot] = od;
				proc.push({od, ot});
			}
		}
		
	}
	
}
 
int running_v[MXN];
int running_u[MXN];
 
bool byd(int a, int b) {
	return dist[a] < dist[b];
}
 
void go(int from, int to) {
	
	src(from);
	
	vector<int> proc;
	for (int i=1; i<=n; i++) proc.push_back(i);
	
	sort(proc.begin(), proc.end(), byd);
	
	for (auto no: proc) {
		
		running_v[no] = distv[no];
		running_u[no] = distu[no];
		
		for (auto x: adj[no]) {
			int ot = x.first;
			int od = x.second;
			if (dist[ot] + od == dist[no]) {
				running_u[no] = min(running_u[no], running_u[ot]);
				running_v[no] = min(running_v[no], running_v[ot]);
			}
		}
		
		if (access[no]) {
			result = min(result, running_u[no] + distv[no]);
			result = min(result, distu[no] + running_v[no]);
		}
		
	}
	
}
 
signed main() {
 
	cin >> n >> m;
	cin >> s >> t;
	cin >> u >> v;
	
	for (int i=0; i<m; i++) {
		int a, b, w;
		cin >> a >> b >> w;
		adj[a].push_back({b, w});
		adj[b].push_back({a, w});
	}
	
	src(u);
	for (int i=1; i<=n; i++) distu[i] = dist[i];
	
	src(v);
	for (int i=1; i<=n; i++) distv[i] = dist[i];
	
	result = distu[v];
	
	src(s);
	for (int i=1; i<=n; i++) dists[i] = dist[i];
	
	src(t);
	for (int i=1; i<=n; i++) distt[i] = dist[i];
	
	for (int i=1; i<=n; i++) {
		if (dists[i] + distt[i] == dists[t]) {
			access[i] = true;
		}
	}
	
	go(s, t);
	go(t, s);
	
	cout << result << endl;
 
}

Compilation message (stderr)

commuter_pass.cpp: In function 'void usaco()':
commuter_pass.cpp:18:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |  freopen("problem.in", "r", stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:19:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |  freopen("problem.out", "w", stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45