Cod sursa(job #2112684)

Utilizator Dobricean_IoanDobricean Ionut Dobricean_Ioan Data 23 ianuarie 2018 19:16:23
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.26 kb
// Alg lui Dijkstra  O(M * log n)
// determina sirul d[] (d[x] = dist minima de la nodul sursa S, la nodul x)
#include <fstream>
#include <vector>
#include <queue>
using namespace std;

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

const int MaxN = 101, Inf = 0x3f3f3f3f;

using PII = pair<int, int>;
using VI = vector<int>;
using VB = vector<bool>;
using VP = vector<PII>;
using VVP = vector<VP>;

VVP G;
VI d;
int n;

void ReadGraph();
void Dijkstra(int S, VI& d);

int main()
{
	ReadGraph();
	Dijkstra(1, d);
	
	for (int i = 2; i <= n; ++i)
		if (d[i] == Inf)
			fout << 0 << ' ';
		else
			fout << d[i] << ' ';
		
	fin.close();
	fout.close();
	
	return 0;
}

void Dijkstra(int x, VI& d) 
{
	priority_queue<PII, VP, greater<PII>> Q;   // min-heap
	d = VI(n + 1, Inf);
	d[x] = 0;
	Q.push({0, x});
	
	int y, w, dx;  // distanta cu care iese x din coada 
	while (!Q.empty())
	{
		x = Q.top().second; dx = Q.top().first;
		Q.pop();
		if (d[x] < dx)	
			continue;
		for (const PII& p : G[x])
		{
			y = p.first;
			w = p.second;
			if (d[y] > d[x] + w)
			{
				d[y] = d[x] + w;
				Q.push({d[y], y});
			}
		}
		
	}
}

void ReadGraph()
{
	int m;
	fin >> n >> m;
	G = VVP(n + 1); // G[0], G[1]
	int x, y, w;
	while (m--)
	{
		fin >> x >> y >> w;
		G[x].push_back({y, w});
	}
}