Cod sursa(job #381833)

Utilizator GavrilaVladGavrila Vlad GavrilaVlad Data 11 ianuarie 2010 19:44:33
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.86 kb
#include <stdio.h>
#include <vector>
#include <set>
#include <algorithm>

using namespace std;

#define maxn 50010
#define maxm 250010
#define inf 1000000000
#define pb push_back
#define mp make_pair

struct muchie
{
    long a, b, c;
} e[maxm];

long n, m, i, j, k, left, right, cost[maxn], f[maxn];
vector <long> v[maxn];
vector <pair<long, long> > h;

void init()
{
    long i;
    cost[1]=0;
    for(i=2; i<=n; i++)
        cost[i]=inf;
    h.pb(mp(0, 1));
    make_heap(h.begin(), h.end());
}

void solve()
{
    pair<long, long> per;
    long i, j, nod, poz;
    long long pas=0;
    while(h.size() && pas<=1LL*n*m)
    {
        pas++;
        pop_heap(h.begin(), h.end());
        per=h.back();
        h.pop_back();
        nod=per.second;
        f[nod]=0;
        for(j=0; j<v[nod].size(); j++)
        {
            poz=v[nod][j];
            if(cost[e[poz].a]+e[poz].c<cost[e[poz].b])
            {
                cost[e[poz].b]=cost[e[poz].a]+e[poz].c;
                if(!f[e[poz].b])
                {
                    f[e[poz].b]=1;
                    h.pb(mp(-cost[e[poz].b], e[poz].b));
                    push_heap(h.begin(), h.end());
                }
            }
        }
    }
}   

long check_negativ()
{
    long i;
    for(i=1; i<=m; i++)
        if(cost[e[i].a]+e[i].c<cost[e[i].b])
            return 1;
    return 0;
}         

int main()
{
    freopen("bellmanford.in", "r", stdin);
    freopen("bellmanford.out", "w", stdout);
    scanf("%d%d", &n, &m);
    for(i=1; i<=m; i++)
    {
        scanf("%d%d%d", &e[i].a, &e[i].b, &e[i].c);
        v[e[i].a].pb(i);
    }
    init();
    solve();
    if(check_negativ())
    {
        printf("Ciclu negativ!\n");
        return 0;
    }
    for(i=2; i<=n; i++)
        printf("%d ", cost[i]);
    return 0;
}