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Cod sursa(job #910994)
#include <fstream>
#define INF 2000000
#define NMAX 50001
using namespace std;
ifstream fin("dijkstra.in");
ofstream fout("dijkstra.out");
struct Arc {int vf; int c;};
int n, x0;
Arc G[15001][15001];
int dmin[NMAX];//distantele minime
int prec[NMAX];//pot reconstitui drumul
int M[NMAX];//multimea vf selectate
int h[NMAX], lgh;//in h sunt vf organiate ca min-heap
int poz[NMAX];//poz[i]=-1 daca vf i nu a fost pus in heap, respectiv 1 daca e pus in heap
void citire();
void afisare();
void dijkstra();
void InsertHeap(int vf);
void Upgrade(int fiu);
int ExtractMin();
void adauga_arc(int x, int y, int cost);
int main()
{
citire();
dijkstra();
afisare();
return 0;
}
void citire()
{
int i, m, x, y, cost;
fin>>n>>m; x0=1;
for(i=0;i<m;i++)
{
fin>>x>>y>>cost;
adauga_arc(x, y, cost);
}
}
void adauga_arc(int x, int y, int cost)
{
G[x][0].vf++;
G[x][G[x][0].vf].c=cost;
G[x][G[x][0].vf].vf=y;
}
void dijkstra()
{
int vfmin, i, j, nrs=1;
for(i=1;i<=n;i++)
{
dmin[i]=INF; prec[i]=x0; poz[i]=-1;
}
//x0 intra in heap pe poz 1
dmin[x0]=0; prec[x0]=-1; poz[x0]=1; h[1]=x0; lgh=1;
while(nrs<n)
{
vfmin=ExtractMin();
M[vfmin]=1; nrs++;
//parcurg lista de adiacenta a lui vfmin
for(j=1;j<=G[vfmin][0].vf;j++)
if(!M[G[vfmin][j].vf])//nu a fost deja selectat
if(dmin[G[vfmin][j].vf]>dmin[vfmin]+G[vfmin][j].c)
{
dmin[G[vfmin][j].vf]=dmin[vfmin]+G[vfmin][j].c;
prec[G[vfmin][j].vf]=vfmin;
if(poz[G[vfmin][j].vf]==-1)//acest vecin nu e selectat
InsertHeap(G[vfmin][j].vf);
else
Upgrade(poz[G[vfmin][j].vf]); //il promovez
}
}
}
void Upgrade(int fiu)
{
int tata=fiu/2,aux;
while(tata && dmin[tata]>dmin[fiu])
{
poz[h[fiu]]=tata; poz[h[tata]]=fiu;
aux=h[fiu]; h[fiu]=h[tata]; h[tata]=aux;
fiu=tata;
tata=fiu/2;
}
}
void InsertHeap(int vf)
{
h[++lgh]=vf;
poz[vf]=lgh;
Upgrade(lgh);
}
int ExtractMin()
{
int fiu,tata,aux;
int minim=h[1];
h[1]=h[lgh--]; poz[h[1]]=-1;
//downgrade
tata=1; fiu=2*tata;
while(fiu<=lgh)
{
if(fiu<lgh&&dmin[h[fiu]]>dmin[h[fiu+1]]) fiu++;
if(dmin[h[tata]]>dmin[h[fiu]])
{
poz[h[fiu]]=tata; poz[h[tata]]=fiu;
aux=h[fiu]; h[fiu]=h[tata]; h[tata]=aux;
tata=fiu;
fiu=2*tata;
}
else break;
}
return minim;
}
void afisare()
{
int i;
for(i=2;i<=n;i++)
{
if(dmin[i]==INF)
fout<<0<<' ';
else
fout<<dmin[i]<<' ';
}
fout<<'\n';
fout.close();
}