Mai intai trebuie sa te autentifici.
Cod sursa(job #910984)
| Utilizator | Data | 11 martie 2013 11:13:40 | |
|---|---|---|---|
| Problema | Algoritmul lui Dijkstra | Scor | 0 |
| Compilator | cpp | Status | done |
| Runda | Arhiva educationala | Marime | 2.6 kb |
#include <fstream>
#define NMAX 1001
#define INF 99999999
using namespace std;
ifstream fin("dj.in");
ofstream fout("dj.out");
struct arc
{
int vf; int c;
} g[NMAX][NMAX];
void citire();
void dijkstra();
void Insert_heap(int vf);
void Upgrade(int fiu);
int extract_min();
void afisare();
int cmin[NMAX];
int tata[NMAX],M[NMAX];
int h[NMAX]; //heap-ul
int sol[NMAX];
int n,m,x0;
int poz[NMAX]; //va fi -1 daca varful nu a fost pus in heap
int lgh;
int main()
{
citire();
dijkstra();
afisare();
fout.close();
return 0;
}
void afisare()
{
int i;
for(i=2;i<=n;i++)
fout<<cmin[i]<<' ';
fout<<'\n';
}
void adauga_arc(int x,int y,int c)
{
g[x][0].c++;
g[x][g[x][0].c].vf=y;
g[x][g[x][0].c].c=c;
}
void citire()
{
int i,j,x,y,z;
fin>>n>>m; // citim nr de varfuri, de arce si varful de start
x0=1;M[x0]=1;
for(i=1;i<=m;i++)
{
// citim si punem costurile in matrice
fin>>x>>y>>z;
adauga_arc(x,y,z);
}
}
void dijkstra()
{
int i,j,nrs=1,vfmin;
for(i=1;i<=n;i++)
cmin[i]=INF,tata[i]=x0,poz[i]=-1;
cmin[x0]=0;
tata[x0]=-1;
poz[x0]=1;
h[1]=x0;
lgh=1;
while(nrs<n)
{
vfmin=extract_min();
M[vfmin]=1;// adaugam in multimea varfurilor vizitate deja varful curent
nrs++;
for(j=1;j<=g[vfmin][0].c;j++) //actualizam costurile daca exista o varianta mai buna
if(!M[g[vfmin][j].vf] && cmin[g[vfmin][j].vf]>cmin[vfmin]+g[vfmin][j].c)
{
cmin[g[vfmin][j].vf]=cmin[vfmin]+g[vfmin][j].c;
tata[g[vfmin][j].vf]=vfmin;
if(poz[g[vfmin][j].vf]==-1)
Insert_heap(g[vfmin][j].vf);
else
Upgrade(poz[g[vfmin][j].vf]);
}
}
}
int extract_min()
{
int fiu,tata,aux;
int minim=h[1];
h[1]=h[lgh--];poz[h[1]]=-1;
while(fiu<=lgh)
{
if(fiu<lgh && cmin[h[fiu]]>cmin[h[fiu+1]]) fiu++;
if(cmin[h[tata]]>cmin[h[fiu]])
{
poz[h[fiu]]=tata;
poz[h[tata]]=fiu;
aux=h[fiu];h[fiu]=h[tata];h[tata]=aux;
tata=fiu;
fiu=tata*2;
}
else
break;
}
return minim;
}
void Insert_heap(int vf)
{
h[++lgh]=vf;
poz[vf]=lgh;
Upgrade(lgh);
}
void Upgrade(int fiu)
{
int tata=fiu/2, aux;
while(tata && cmin[tata]>cmin[fiu])
{
poz[h[fiu]]=tata;
poz[h[tata]]=fiu;
aux=h[fiu];h[fiu]=h[tata];h[tata]=aux;
fiu=tata;
tata=fiu/2;
}
}
