Cod sursa(job #594886)

Utilizator nandoLicker Nandor nando Data 10 iunie 2011 12:18:57
Problema Algoritmul lui Dijkstra Scor 90
Compilator cpp Status done
Runda Arhiva educationala Marime 1.84 kb
#include <cstdio>
#include <vector>
#include <bitset>
using namespace std;

#define MAX 50005
#define INF 0x3f3f3f3f

//<parsing>
FILE* fin=fopen("dijkstra.in","r");
const unsigned maxb=8192;
char buf[maxb];
unsigned ptr=maxb;

inline unsigned getInt(){
	unsigned nr=0;
	while(buf[ptr]<'0'||'9'<buf[ptr])
		if(++ptr>=maxb)
			fread(buf,maxb,1,fin),ptr=0;
	while('0'<=buf[ptr]&&buf[ptr]<='9'){
		nr=nr*10+buf[ptr]-'0';
		if(++ptr>=maxb)
			fread(buf,maxb,1,fin),ptr=0;
	}
	return nr;
}
//</parsing>

typedef vector<pair<int,int> >::iterator iter;
int n,m,heap[MAX],poz[MAX],d[MAX],l;
vector<pair<int,int> > g[MAX];
bitset<MAX> viz;
#define min(a,b) (((a)<(b))?(a):(b))

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=1;i<=n;i++){
		d[i]=INF;
		heap[i]=poz[i]=i;
	}

	d[1]=0,l=n;

	while(l){
		int top=heap[1];
		viz[heap[1]]=true;
		swapH(1,l);
		l--;
		downHeap(1);

		for(iter it=g[top].begin();it!=g[top].end();it++){
			if(!viz[it->first]&&(d[it->first]>d[top]+it->second)){
				d[it->first]=d[top]+it->second;
				upHeap(poz[it->first]);
			}
		}
	}
}

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

	n = getInt (), m = getInt ();

	int x,y,c;

	for(int i=0;i<=m;i++){
        x = getInt (), y = getInt (), c = getInt ();
		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]);
	}

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