Submission #103355

#	Time	Username	Problem	Language	Result	Execution time	Memory
103355		tincamatei	Commuter Pass (JOI18_commuter_pass)	C++14	0 / 100	2050 ms	18604 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 100000;
const long long INF = 1LL << 60;

vector<pair<int, int> > graph[1+MAX_N];

long long dist[2][1+MAX_N], dists[1+MAX_N];
long long dp[1+MAX_N][2];

void dijkstra(int n, int src, long long *dist) {
	priority_queue<pair<long long, int> > pq;

	for(int i = 1; i <= n; ++i)
		dist[i] = INF;
	
	dist[src] = 0;
	pq.push(make_pair(0, src));
	
	while(!pq.empty()) {
		int nod = pq.top().second;
		long long cost = -pq.top().first;
		pq.pop();

		if(cost == dist[nod]) {
			for(auto it: graph[nod])
				if(cost + it.second < dist[it.first]) {
					dist[it.first] = cost + it.second;
					pq.push(make_pair(-cost - it.second, it.first));
				}
		}
	}
}

void computeDp(int nod) {
	dp[nod][0] = dp[nod][1] = INF;

	for(auto it: graph[nod])
		if(dists[nod] - it.second == dists[it.first]) {
			computeDp(it.first);
			for(int i = 0; i < 2; ++i)
				dp[nod][i] = min(dp[nod][i], dp[it.first][i]);
		}
	
	for(int i = 0; i < 2; ++i)
		dp[nod][i] = min(dp[nod][i], dist[i][nod]);
}

int main() {
#ifdef HOME
	FILE *fin = fopen("input.in", "r");
	FILE *fout = fopen("output.out", "w");
#else
	FILE *fin = stdin;
	FILE *fout = stdout;
#endif

	int n, m, s, t, u, v;
	int a, b, c;

	fscanf(fin, "%d%d%d%d%d%d", &n, &m, &s, &t, &u, &v);
	for(int i = 0; i < m; ++i) {
		fscanf(fin, "%d%d%d", &a, &b, &c);
		graph[a].push_back(make_pair(b, c));
		graph[b].push_back(make_pair(a, c));
	}

	dijkstra(n, u, dist[0]);
	dijkstra(n, v, dist[1]);
	dijkstra(n, s, dists);
	
	computeDp(t);
	
	fprintf(fout, "%lld", dp[t][0] + dp[t][1]);

	fclose(fin);
	fclose(fout);
	return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:63:8: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  fscanf(fin, "%d%d%d%d%d%d", &n, &m, &s, &t, &u, &v);
  ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:65:9: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   fscanf(fin, "%d%d%d", &a, &b, &c);
   ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 16
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45