Cod sursa(job #566895)

Utilizator BalcauIonutFMI-Balcau Ionut BalcauIonut Data 29 martie 2011 13:28:44
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.54 kb
#include <vector>
#include <cstdio>
#include <queue>
#include <bitset>
using namespace std;
const int INF=1<<30;

int n,m;
bool negative=false;
vector< pair<int,int> > a[50005];
int dist[50005];
int cycle[50005];
void readData(){
    int i,x,y,c;
    freopen("bellmanford.in","r",stdin);
    scanf("%d %d",&n,&m);
    for(i=0;i<m;++i){
        scanf("%d %d %d",&x,&y,&c);
        a[x].push_back(make_pair(y,c));
    }
}

void bellmanFord(){
    queue< int > q; int x,i,j,c;
    bitset< 50005 > inq(false);
    for(i=2;i<=n;++i)
        dist[i]=INF;
    dist[1]=0;
    q.push(1);
    inq[1]=true;
    while(!q.empty() && !negative){
        x=q.front();
        q.pop();
        inq[x]=false;
        for(i=0;i<a[x].size();++i){
            j=a[x][i].first; c=a[x][i].second;
            if(dist[x]+c<dist[j]){
                dist[j]=dist[x]+c;
                if(!inq[j]){
                    if(cycle[j]>n)
                        negative=true;
                    q.push(j);
                    cycle[j]++;
                    inq[j]=true;
                }
            }
        }
    }
}

void writeData(){
    int i;
    freopen("bellmanford.out","w",stdout);
    if(!negative)
        for(i=2;i<=n;++i)
            printf("%d ",dist[i]);
    else printf("Ciclu negativ!");
}

int main(){
    readData();
    bellmanFord();
    writeData();

   /* int i,j;
    for(i=1;i<=n;++i)
        for(j=0;j<a[i].size();++j)
        printf("%d %d %d\n",i,a[i][j].first,a[i][j].second);
    */
    return 0;
}