Cod sursa(job #2196777)

Utilizator al3xionescuIonescu Alexandru al3xionescu Data 20 aprilie 2018 12:51:54
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 2.02 kb
#include<iostream>
#include<fstream>
#include<vector>
#include<algorithm>
#include<cassert>
#include<queue>
#include<bitset>
using namespace std;
const char iname[] = "bellmanford.in";
const char oname[] = "bellmanford.out";
const int MAX_N = 50005;
const int INF = 0x3f3f3f3f;
vector<pair <int, int> > adj[MAX_N];
vector<int> adj_t[MAX_N];

int main()
{
    ifstream in(iname);
    int nodes, edges;
    assert(in>>nodes>>edges);
    assert(1<=nodes && nodes<=50000);
    assert(1<=edges && edges<=250000);
    for(int i=0;i<edges;i++){
        int x,y,c;
        assert(in>>x>>y>>c);
        assert(1<=x && x<=nodes);
        assert(1<=y && y<=nodes);
        assert(-1000<=c && c<=1000);
        adj[x].push_back(make_pair(y,c));
        assert(find(adj_t[x].begin(),adj_t[x].end(),y)==adj_t[x].end());
        adj_t[x].push_back(y);
    }
    in.close();
    queue<int> Q;
    bitset<MAX_N> in_queue = false;
    vector<int> dist(MAX_N,INF), cnt_in_queue(MAX_N,0);
    int negative_cycle = false;
    dist[1] = 0,Q.push(1), in_queue[1].flip();
    while(!Q.empty() && !negative_cycle) {
        int x = Q.front();
        Q.pop();
        in_queue[x] = false;
        vector < pair <int, int> >::iterator it;
        for (it = adj[x].begin(); it != adj[x].end(); ++ it) if (dist[x] < INF)
            if (dist[it->first] > dist[x] + it->second) {
                dist[it->first] = dist[x] + it->second;
                if (!in_queue[it->first]) {
                    if (cnt_in_queue[it->first] > nodes)
                        negative_cycle = true;
                    else {
                        Q.push(it->first);
                        in_queue[it->first] = true;
                        cnt_in_queue[it->first] ++;
                    }
                }
            }
    }
    ofstream out(oname);
    if(!negative_cycle) {
        for(int i=2;i<=nodes;i++)
            out<<dist[i]<<' ';
    }
    else{
        out<<"Ciclu negativ!";
    }
    out.close();



    return 0;
}