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Cod sursa(job #486495)
#include<stdio.h>
#include<vector>
#define inf 2000000000
FILE *f=fopen("dijkstra.in","r");
FILE *g=fopen("dijkstra.out","w");
using namespace std;
int n,m,k,i,x,y,z,j,heapn;
int minim,p;
int s[50001],dest[50001],mymin[50001];
pair<int,int> d[50001]; //first=cost,second=dest
vector< pair<int,int> > a[50001]; //first=dest,second=cost
void downheap(int p){
int l,r;
while(2*p<=heapn){
minim=p;
l=2*p;
r=2*p+1;
if(d[minim].first>d[l].first)
minim=l;
if(r<=heapn&&d[minim].first>d[r].first)
minim=r;
if(minim!=p){
pair<int,int> t=d[p];
d[p]=d[minim];
d[minim]=t;
int x=dest[d[p].second];
dest[d[p].second]=dest[d[minim].second];
dest[d[minim].second]=x;
}
else break;
}
}
void upheap(int p){
int t;
while(p>1){
t=p/2;
if(d[p].first<d[t].first){
pair<int,int> m=d[p];
d[p]=d[t];
d[t]=m;
int x=dest[d[p].second];
dest[d[p].second]=dest[d[t].second];
dest[d[t].second]=x;
p=t;
}
else break;
}
}
int main(){
//citire
fscanf(f,"%d%d",&n,&m);
for(i=1;i<=m;i++){
fscanf(f,"%d%d%d",&x,&y,&z);
a[x].push_back(make_pair(y,z));
}
//d=inf,mymin=inf,dest=0
for(i=0;i<=n;i++){
d[i].first=inf;
mymin[i]=inf;
dest[i]=0;
}
//d[i] = distanta de la nod[1] la nod[i]
for(i=0;i<=(int)a[1].size()-1 ;i++){
heapn++;
d[heapn].first=a[1][i].second;
d[heapn].second=a[1][i].first;
dest[a[1][i].first]=heapn;
upheap(heapn);
}
//selectam primul nod
s[1]=1;
//rezolvare Nlog(N)
while(heapn){
p=d[1].second;
int cost=d[1].first;
//stergem primul element si reactualizam heapul
d[1]=d[heapn];
heapn--;
dest[d[1].second]=1;
downheap(1);
//salvam costul minim pentru nodul eliminat
if(mymin[p]>cost)
mymin[p]=cost;
s[p]=1;
//minimul pana la toti vecinii
for(i=0;i<=(int)a[p].size()-1;i++)
//daca vecinul nu a fost selectat si costul este mai mic
if(s[a[p][i].first]==0 && cost +a[p][i].second < d[dest[a[p][i].first]].first ){
//daca vecinul exista in heap
if(dest[a[p][i].first]!=0)
d[dest[a[p][i].first]].first=cost+a[p][i].second;
//daca nu, il adaugam
else {
heapn++;
d[heapn].first=cost+a[p][i].second;
d[heapn].second=a[p][i].first;
dest[a[p][i].first]=heapn;
upheap(heapn);
}
if(mymin[a[p][i].first] > cost+a[p][i].second)
mymin[a[p][i].first] = cost+a[p][i].second;
}
dest[p]=-1;
}
//afisam
for(i=2;i<=n;i++){
if(mymin[i]!=inf)
fprintf(g,"%d ",mymin[i]);
else fprintf(g,"%d ",0);
}
return 0;
}