Cod sursa(job #1516963)

Utilizator tudormaximTudor Maxim tudormaxim Data 3 noiembrie 2015 19:05:29
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.84 kb
#include <fstream>
#include <vector>
#include<limits.h>
using namespace std;
ifstream fin("dijkstra.in");
ofstream fout("dijkstra.out");
const int NMax = 50001;
const int INF = INT_MAX;
int n, m, nh;
int d[NMax];
int h[NMax];
int poz[NMax];
struct muchie{ int y,cost; };
vector <muchie> a[NMax];

void schimba(int i1, int i2)
{
    int aux = h[i1];
    h[i1] = h[i2];
    h[i2] = aux;

    poz[h[i1]] = i1;
    poz[h[i2]] = i2;
}

void urca(int i)
{
    while( i>1 && d[h[i]] < d[h[i/2]])
    {
        schimba(i, i/2);
        i/=2;
    }
}

void coboara(int i)
{
    int bun=i, fs=i*2, fd=i*2+1;

    if(fs<=nh && d[h[fs]] < d[h[bun]])
        bun=fs;
    if(fd<=nh && d[h[fd]] < d[h[bun]])
        bun=fd;

    if(i!=bun)
    {
        schimba(i, bun);
        coboara(bun);
    }
}

void adauga(int x)
{
    h[++nh]=x;
    poz[x]=nh;
    urca(nh);
}

void sterge(int i)
{
    schimba(i, nh);
    nh--;
    coboara(i);
    urca(i);
}

void init(int x)
{
    nh=0;
    for(int i=1; i<=n; i++){
        d[i]=INF;
    }
    d[x]=0;
    adauga(x);
}

int dijkstra(int x)
{
    init(x);
    while(nh!=0)
    {
        x = h[1];
        sterge(1);
        for(size_t i=0; i<a[x].size(); i++)
        {
            int y=a[x][i].y;
            int cost=a[x][i].cost;
            if(d[x] + cost < d[y])
            {
                d[y] = d[x]+cost;
                if(poz[y] == 0) adauga(y);
                else urca(poz[y]);
            }
        }
    }
}

int main ()
{
    int x, y, cost, i;
    fin >> n >> m;
    for(i=1; i<=m; i++)
    {
        fin >> x >> y >>cost;
        a[x].push_back(muchie{y, cost});
    }
    dijkstra(1);
    for(int i=2; i<=n; i++)
    {
        if(d[i] == INF) fout << 0 << ' ';
        else fout << d[i] << ' ';
    }
    return 0;
}