Cod sursa(job #743925)

Utilizator mihai995mihai995 mihai995 Data 6 mai 2012 19:52:49
Problema Algoritmul lui Dijkstra Scor 10
Compilator cpp Status done
Runda Arhiva educationala Marime 2.42 kb
#include <fstream>
#include <cstring>
#include <vector>
using namespace std;

const int N = 50005, M = 250005, inf = 0x3f3f3f3f;

int dist[N], n;
bool use[N];

struct Nod
{
    int x, cost;

    Nod()
    {

    }

    Nod(int _x, int _cost)
    {
        x = _x;
        cost = _cost;
    }

    inline bool operator< (Nod N)
    {
        return cost < N.cost;
    }
};

struct Heap
{
    Nod v[M];
    int size;

    Heap()
    {
        size = 0;
    }

    inline int best(int a, int b)
    {
        return (b > size || v[a] < v[b]) ? a : b;
    }

    inline void sch(Nod& a, Nod& b)
    {
        Nod aux = a;
        a = b;
        b = aux;
    }

    void up(int x)
    {
        while (x > 1 && v[x] < v[x >> 1])
        {
            sch(v[x], v[x >> 1]);
            x >>= 1;
        }
    }

    void down(int x)
    {
        int m;
        while (x <= size)
        {
            m = best(x << 1, (x << 1) + 1);

            if (v[m] < v[x])
                return;
            sch(v[x], v[m]);
            x = m;
        }
    }

    void push(int x)
    {
        v[++size] = Nod(x, dist[x]);
        up(size);
    }

    int top()
    {
        return v[1].x;
    }

    void pop()
    {
        v[1] = v[ size-- ];
        down(1);
    }

    inline bool empty()
    {
        return !size;
    }
};

vector<Nod> graph[N];

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

void dijkstra(int x)
{
    int y, upt;
    Heap H;

    memset(dist, inf, sizeof(dist));
    memset(use, false, sizeof(use));

    dist[x] = 0;
    H.push(x);

    while (!H.empty())
    {
        x = H.top(); H.pop();

        if (use[x])
            continue;

        use[x] = true;

        for (vector<Nod> :: iterator it = graph[x].begin() ; it != graph[x].end() ; it++)
        {
            y = (*it).x;
            upt = dist[x] + (*it).cost;
            if (upt < dist[y])
            {
                dist[y] = upt;
                H.push(y);
            }
        }
    }
}

int main()
{
    int m, x, y, c;

    in >> n >> m;

    while (m--)
    {
        in >> x >> y >> c;
        graph[x].push_back(Nod(y, c));
        graph[y].push_back(Nod(x, c));
    }

    dijkstra(1);

    for (int i = 2 ; i <= n ; i++)
        out << (dist[i] != inf ? dist[i] : 0) << " ";

    out << "\n";

    return 0;
}