Cod sursa(job #440575)

Utilizator nandoLicker Nandor nando Data 12 aprilie 2010 10:37:32
Problema Algoritmul lui Dijkstra Scor 20
Compilator cpp Status done
Runda Arhiva educationala Marime 1.49 kb
#include <cstdio>
#include <vector>
using namespace std;

#define MAX 50000
#define INF 0x3f3f3f3f

typedef vector<pair<int,int> >::iterator iter;
int n,m,heap[MAX],poz[MAX],d[MAX],l;
vector<pair<int,int> > g[MAX];

void swapH(int a,int b){
	int aux=heap[a];
	heap[a]=heap[b];
	heap[b]=aux;

	poz[heap[a]]=a;
	poz[heap[b]]=b;
}

void upHeap(int k){
	while( (k>>1) && d[heap[k>>1]]>d[heap[k]] ){
		swapH(k,k>>1);
		k>>=1;
	} 
}

void downHeap(int p){
	int q=0;
	while(q!=p){
		q=p;
		if((q>>1)<=l && d[heap[q>>1]] < d[heap[p]] ) p=q>>1;
		if((q>>1)+1<=l && d[heap[q>>1+1]] < d[heap[p]] ) p=(q>>1)+1;

		swapH(p,q);
	}
}

void dijkstra(){
	for(int i=2;i<=n;i++){
		d[i]=INF,poz[i]=-1;
	}

	d[1]=0,heap[1]=1,l=1;

	while(l){

		int min=heap[1];
		poz[heap[1]]=1;
		swapH(1,l),l--;
		downHeap(1);

		for(iter it=g[min].begin();it!=g[min].end();it++){
			if(d[min]+it->second<d[it->first]){
				d[it->first]=d[min]+it->second;
			}
			if(poz[it->first]!=-1){
				upHeap(poz[it->first]);
			}else{
				heap[++l]=it->first;
				poz[heap[l]]=l;
				upHeap(l);
			}
		}
	}
}

int main(){
	FILE* fin=fopen("dijkstra.in","r");
	FILE* fout=fopen("dijkstra.out","w");

	fscanf(fin,"%d %d\n",&n,&m);
	int x,y,c;

	for(int i=0;i<=m;i++){
		fscanf(fin,"%d %d %d\n",&x,&y,&c);
		g[x].push_back(make_pair(y,c));
	}

	dijkstra();

	for(int i=2;i<=n;i++){
		fprintf(fout,"%d ",(d[i]==INF)?0:d[i]);
	}

	getchar();

	fclose(fin);
	fclose(fout);
	return 0;
}