hdoj 1142 A Walk Through the Forest

/*
HDOJ: 1142 A Walk Through the Forest
*/
#include <iostream>
#include <cstdio>
#include <cstring>

#define MaxD (1 << 20)
#define MaxN (1 << 10)

using namespace std;

long map[MaxN][MaxN];
bool visited[MaxN];
long dis[MaxN];
long long res[MaxN];
int n, m;

void Dijkstra(int v);
long long solve(int v);

int main()
{
//freopen("data.in", "rb", stdin);
while(scanf("%d", &n) != EOF && n) {
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= n; j++) {
map[i][j] = i == j ? 0 : MaxD;
}
}
scanf("%d", &m);
for(int i = 0; i < m; i++) {
int a, b, c;
scanf("%d%d%d", &a, &b, &c);
map[a][b] = map[b][a] = c;
}

Dijkstra(2);

memset(res, -1, sizeof(res));

printf("%lld\n", solve(1));
}

return 0;
}

void Dijkstra(int v)
{
for(int i = 1; i <= n; i++) {
visited[i] = false;
dis[i] = map[2][i];
}
visited[2] = true;
dis[2] = 0;

for(int i = 2; i <= n; i++) {
int tmp = MaxD;
int tmp_index = 0;
for(int j = 1; j <= n; j++) {
if(!visited[j] && dis[j] < tmp) {
tmp = dis[j];
tmp_index = j;
}
}

visited[tmp_index] = true;

for(int k = 1; k <= n; k++) {
if(!visited[k] && dis[k] > dis[tmp_index] + map[k][tmp_index]) {
dis[k] = dis[tmp_index] + map[k][tmp_index];
}
}
}
}

long long solve(int v)
{
if(res[v] != -1)
return res[v];

if(v == 2)
return 1;

res[v] = 0;
for(int i = 1; i <= n; i++) {
if(map[i][v] != MaxD && dis[i] < dis[v])
res[v] += solve(i);
}

return res[v];
}