Cod sursa(job #2225887)

Utilizator Horia14Horia Banciu Horia14 Data 28 iulie 2018 15:42:24
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 2.07 kb
#include<cstdio>
#include<cctype>
#include<vector>
#include<queue>
#define MAX_N 50000
#define BUF_SIZE 1 << 19
#define oo 0x3f3f3f3f
using namespace std;

vector<pair<int,int> >g[MAX_N+1];
int dist[MAX_N+1], cnt[MAX_N+1], n, m, pos = BUF_SIZE;
bool used[MAX_N+1], cycle;
char buf[BUF_SIZE];
queue<int>q;

inline char getChar(FILE* fin) {
    if(pos == BUF_SIZE) {
        fread(buf,1,BUF_SIZE,fin);
        pos = 0;
    }
    return buf[pos++];
}

inline int read(FILE* fin) {
    int semn ,res = 0;
    char c;
    semn = 1;
    do {
        c = getChar(fin);
        if(c == '-')
            semn = -semn;
    }while(!isdigit(c));
    do {
        res = 10*res + c - '0';
        c = getChar(fin);
    }while(isdigit(c));
    return res * semn;
}

void readGraph() {
    int i, x, y, cost;
    FILE* fin = fopen("bellmanford.in","r");
    n = read(fin); m  = read(fin);
    for(i = 0; i < m; i++) {
        x = read(fin); y = read(fin); cost = read(fin);
        g[x].push_back(make_pair(y,cost));
    }
    fclose(fin);
}

void bellmanFord(int x) {
    vector<pair<int,int> >::iterator it;
    int i, node;
    for(i = 1; i <= n; i++)
        dist[i] = oo;
    dist[x] = 0;
    q.push(x);
    used[x] = true;
    while(!q.empty() && !cycle) {
        node = q.front();
        q.pop();
        used[node] = false;
        for(it = g[node].begin(); it != g[node].end(); it++) {
            if(dist[(*it).first] > dist[node] + (*it).second) {
                dist[(*it).first] = dist[node] + (*it).second;
                if(!used[(*it).first]) {
                    used[(*it).first] = true;
                    q.push((*it).first);
                    if(++cnt[(*it).first] > n)
                        cycle = true;
                }
            }
        }
    }
}

void printDistances() {
    FILE* fout = fopen("bellmanford.out","w");
    bellmanFord(1);
    if(!cycle) {
        for(int i = 2; i <= n; i++)
            fprintf(fout,"%d ",dist[i]);
        fprintf(fout,"\n");
    }
    else fprintf(fout,"Ciclu negativ!\n");
    fclose(fout);
}

int main() {
    readGraph();
    printDistances();
    return 0;
}