Cod sursa(job #2242567)

Utilizator Horia14Horia Banciu Horia14 Data 18 septembrie 2018 22:05:26
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 2.27 kb
#include<cstdio>
#include<vector>
#include<cctype>
#define MAX_N 50000
#define oo 0x3f3f3f3f
#define BUF_SIZE 1 << 18
using namespace std;

vector<pair<int,int> >g[MAX_N+1];
int dist[MAX_N+1], h[MAX_N+1], poz[MAX_N+1], n, m, heapSize, pos = BUF_SIZE;
char buf[BUF_SIZE];

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 res = 0;
    char ch;
    do {
        ch = getChar(fin);
    }while(!isdigit(ch));
    do {
        res = 10*res + ch - '0';
        ch = getChar(fin);
    }while(isdigit(ch));
    return res;
}

void readGraph() {
    int x, y, c;
    FILE* fin = fopen("dijkstra.in","r");
    n = read(fin);
    m = read(fin);
    for(int i = 1; i <= m; i++) {
        x = read(fin);
        y = read(fin);
        c = read(fin);
        g[x].push_back(make_pair(y,c));
    }
    fclose(fin);
}

inline void Swap(int i, int j) {
    int aux = h[i];
    h[i] = h[j];
    h[j] = aux;
    aux = poz[h[i]];
    poz[h[i]] = poz[h[j]];
    poz[h[j]] = aux;
}

void heapDown(int i) {
    int l, r, p;
    l = 2 * i;
    r = 2 * i + 1;
    if(l <= heapSize && dist[h[l]] < dist[h[i]])
        p = l;
    else p = i;
    if(r <= heapSize && dist[h[r]] < dist[h[p]])
        p = r;
    if(p != i) {
        Swap(i,p);
        heapDown(p);
    }
}

void heapUp(int i) {
    while(dist[h[i]] < dist[h[i/2]]) {
        Swap(i,i/2);
        i >>= 1;
    }
}

void Dijkstra(int s) {
    int node;
    for(int i = 1; i <= n; i++) {
        dist[i] = oo;
        h[i] = i;
        poz[i] = i;
    }
    dist[s] = 0;
    heapSize = n;
    for(int j = 1; j <= n - 1; j++) {
        node = h[1];
        Swap(1,heapSize);
        heapSize--;
        heapDown(1);
        for(auto i : g[node]) {
            if(dist[i.first] > dist[node] + i.second) {
                dist[i.first] = dist[node] + i.second;
                heapUp(poz[i.first]);
            }
        }
    }
}

void printDistances() {
    FILE* fout = fopen("dijkstra.out","w");
    for(int i = 2; i <= n; i++)
        if(dist[i] != oo)
            fprintf(fout,"%d ",dist[i]);
        else fprintf(fout,"0 ");
    fprintf(fout,"\n");
    fclose(fout);
}

int main() {
    readGraph();
    Dijkstra(1);
    printDistances();
    return 0;
}