Cod sursa(job #579817)

Utilizator aloneForever Alone alone Data 12 aprilie 2011 14:56:56
Problema Algoritmul lui Dijkstra Scor 80
Compilator cpp Status done
Runda Arhiva educationala Marime 1.79 kb
#include <cstdio>
#include <vector>

using namespace std;

#define NMAX 50050
#define INF 0x3f3f3f3f

int H[NMAX], C[NMAX], poz[NMAX], N, n, m;
vector < pair <short int, short int> > G[NMAX];

void up_heap (int), down_heap (int), dijkstra (), citire (), afisare ();

int main () {
	
	citire ();
	
	dijkstra ();
	
	afisare ();
	
	return 0;
}

void up_heap (int k) {
	
	int c = k, t = c >> 1;
	
	while (t > 0 && C[ H[c] ] < C[ H[t] ]) {
		swap (H[c], H[t]);
		poz[ H[c] ] = c, poz[ H[t] ] = t;
		
		c = t, t = c >> 1;
	}
}

void down_heap (int k) {
	
	int t = k, c = t << 1;
	
	if (c < N && C[ H[c+1] ] < C[ H[c] ]) c++;
	
	while (c <= N && C[ H[c] ] < C[ H[t] ]) {
		swap (H[c], H[t]);
		poz[ H[c] ] = c, poz[ H[t] ] = t;
		
		t = c, c = t << 1;
		if (c < N && C[ H[c+1] ] < C[ H[c] ]) c++;
	}
}

void dijkstra () {
	
	int nod, fiu, cst;
	vector < pair <short int, short int> >::iterator it;
	
	memset (C, INF, sizeof (C));
	
	N = 1, C[1] = 0, H[1] = 1, poz[1] = 1;
	while (N) {
		nod = H[1]; poz[nod] = -1;
		
		H[1] = H[N], poz[ H[1] ] = 1; N--;
		down_heap (1);
		
		for (it = G[nod].begin (); it != G[nod].end (); it++) {
			fiu = it -> first, cst = it -> second;
			
			if (C[nod] + cst < C[fiu]) {
				C[fiu] = C[nod] + cst;
				
				if (!poz[fiu]) {
					N++, H[N] = fiu, poz[fiu] = N;
					up_heap (N);
				}
				else
					up_heap (poz[fiu]);
			}
		}
	}
}

void citire () {
	
	freopen ("dijkstra.in", "r", stdin);
	
	int i, x, y, c;
	
	scanf ("%d %d", &n, &m);
	
	for (i = 1; i <= m; i++) {
		scanf ("%d %d %d", &x, &y, &c);
		G[x].push_back (make_pair ((short int) y, (short int) c));
	}
}

void afisare () {
	
	freopen ("dijkstra.out", "w", stdout);
	
	for (int i = 2; i <= n; i++)
		printf ("%d ", C[i] != INF ? C[i] : 0);
}