Cod sursa(job #2950069)

Utilizator AkiyoAki Yo Akiyo Data 2 decembrie 2022 18:50:10
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.32 kb
/* Alg lui Dijkstra
 * Complexitate O(n * log(m))
 * Det dist minima de la un nod sursa la nodul  toate celelalte noduri
 *
 */
#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <queue>
#include <tuple>
using namespace std;

ifstream fin("dijkstra.in");
ofstream fout("dijkstra.out");

const int Inf = 0x3f3f3f3f;
using PI  = pair<int, int>;
using VP  = vector<PI>;
using VVP = vector<VP>;
using VI  = vector<int>;

VVP G;
VI d;    // d[x] = dist minima de la nodul sursa la nodul x
int n;
int m;

void ReadGraph();
void Dijkstra(int x, VI& d);
void WriteDistances();

int main()
{
	ReadGraph();
	Dijkstra(1, d);
	WriteDistances();
	return 0;
}

void Dijkstra(int x, VI& d)
{
	priority_queue<PI, vector<PI>, greater<PI>> Q;
	d = VI(n + 1, Inf);
	d[x] = 0;   // x - sursa
	Q.emplace(0, x);

	while (!Q.empty())
	{
		auto [dx, x] = Q.top();
		Q.pop();
		if (dx > d[x]) // daca x a fost anterior in coada
			continue;

		for (auto p : G[x])
		{
			auto [y, w] = p;
			if (d[y] > d[x] + w)
			{
				d[y] = d[x] + w;
				Q.emplace(d[y], y);
			}
		}
	}
}

void ReadGraph()
{
	fin >> n >> m;

	G = VVP(n + 1);
	int x, y, w;

	while (m--)
	{
		fin >> x >> y >> w;
		G[x].emplace_back(y, w);
	}
}

void WriteDistances()
{
	for (int i = 2; i <= n; ++i)
		if (d[i] != Inf)
			fout << d[i] << ' ';
		else
			fout << 0 << ' ';
}