Cod sursa(job #2844146)

Utilizator Horis21Horia Radu Horis21 Data 3 februarie 2022 20:37:15
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 2.03 kb
#include <fstream>
#include <vector>
#define N 50001
#define M 250001
#define INF 1000000001

using namespace std;

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

vector<pair<int,int>> succ[N];
int lst[N], d[N], h[N], pos[N], n, m, nr, nh;

void swap(int p1, int p2)
{
    int aux = h[p1];
    h[p1] = h[p2];
    h[p2] = aux;
    pos[h[p1]] = p1;
    pos[h[p2]] = p2;
}

void add_edge(int x, int y, int c)
{
    pair<int,int> e;
    e.first=y;
    e.second=c;
    succ[x].push_back(e);
}


void up(int p)
{
    while (p > 1 && d[h[p]] < d[h[p/2]])
    {
        swap(p, p/2);
        p /= 2;
    }
}

void down(int p)
{
    int lc = 2*p, rc = 2*p + 1, next = p;
    if (lc <= nh && d[h[lc]] < d[h[next]])
    {
        next = lc;
    }
    if (rc <= nh && d[h[rc]] < d[h[next]])
    {
        next = rc;
    }
    if (next != p)
    {
        swap(next,p);
        down(next);
    }
}

void remove(int p)
{
    if (p == nh)
    {
        nh--;
    }
    else
    {
        h[p] = h[nh--];
        pos[h[p]] = p;
        down(p);
    }
}

void dijkstra(int x0)
{
    for (int i = 1; i <= n; i++)
    {
        d[i] = INF;

    }
    d[x0] = 0;
    h[++nh] = x0;
    pos[x0] = nh;
    while (nh > 0)
    {
        int x = h[1];
        remove(1);
        for (auto p: succ[x])
        {
            int y = p.first;
            int c = p.second;
            if (d[x] + c < d[y])
            {
                d[y] = d[x] + c;
                if (pos[y] == 0)
                {
                    h[++nh] = y;
                    pos[y] = nh;
                }
                up(pos[y]);
            }
        }
    }
}

int main()
{

    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int x, y, c;
        in >> x >> y >> c;
        add_edge(x, y, c);
    }
    dijkstra(1);
    for (int i = 2; i <= n; i++)
    {
        if (d[i] == INF)
        {
            d[i] = 0;
        }
       out << d[i] << " ";
    }
    return 0;
}