OJ-Problems-Source/HDOJ/1142_autoAC.cpp
2016-08-13 10:51:15 +08:00

92 lines
1.8 KiB
C++

#include <cstdio>
#include <queue>
#include <algorithm>
using namespace std;
const int inf = 1000000000;
int map[1010][1010];
int n, p;
bool flag[1010];
int dis[1010];
void spfa()
{
for(int i = 1; i <= n ;++i)
{
flag[i] = false;
dis[i] = inf;
}
dis[2] = 0;
flag[2] = true;
queue<int> que;
que.push(2);
while(!que.empty())
{
int now = que.front();
que.pop();
flag[now] = false;
for(int i = 1; i <= n ;++i)
{
if(dis[i] > dis[now] + map[now][i])
{
dis[i] = dis[now] + map[now][i];
if(!flag[i])
{
flag[i] = true;
que.push(i);
}
}
}
}
}
int cou[1010];
void dfs(int now)
{
if(now == 2)
{
cou[2] = 1;
return;
}
int result(0);
for(int i = 1; i <= n ;++i)
{
if(map[now][i] != inf && dis[i] < dis[now])
{
if(cou[i] >= 0)
{
result += cou[i];
}
else
{
dfs(i);
result += cou[i];
}
}
}
cou[now] = result;
}
int main()
{
int a, b, dist;
while(scanf("%d", &n) != EOF)
{
if(!n)
break;
scanf("%d", &p);
for(int i = 0; i <= n; ++i)
for(int j = 1; j <= n;++j)
map[i][j] = inf;
for(int i= 0; i < p; ++i)
{
scanf("%d %d %d", &a, &b, &dist);
map[a][b] = map[b][a] = dist;
}
spfa();
for(int i = 1; i <= n;++i)
{
cou[i] = -1;
}
dfs(1);
printf("%d\n", cou[1]);
}
return 0;
}