最短路径树计数问题AcWing349

#include <bits/stdc++.h>

using namespace std;
#define ll long long
#define mem(a, b) memset(a,b,sizeof(a))
#define INF 0x3f3f3f3f
#define DBG printf("this is a input\n")
#define fi first
#define se second
#define mk(a, b) make_pair(a,b)
#define p_queue priority_queue

ll gcd(ll a, ll b) {
    return b == 0 ? a : gcd(b, a % b);
}

ll lcm(ll a, ll b) {
    return a / gcd(a, b) * b;
}
const ll mod = 2147483647;
int n , m;
int head[1005] , cnt;
struct e{
    int t, next;
    ll w;
}edge[2000000];
ll dis[1005], vis[1005];
ll dp[1005];
void add(int f , int t, ll w)
{
    edge[cnt].t = t;
    edge[cnt].w = w;
    edge[cnt].next = head[f];
    head[f] = cnt ++;
}
void dijkstra()
{
    mem(dis,INF);
    dis[1] = 0;
    for(int i = 1 ; i <= n ; i ++)
    {
        int minn = INF, index;
        for(int j = 1 ; j <= n ; j ++)
        {
            if(minn > dis[j] && !vis[j])
            {
                index = j;
                minn = dis[j];
            }
        }
        vis[index] = 1;
        for(int j = head[index] ; j != -1 ; j = edge[j].next)
        {
            int v = edge[j].t , w = edge[j].w;
            dis[v] = min(dis[v],dis[index] + w);
        }
    }
}
int main(void)
{
    mem(head,-1);
    cin>>n>>m;
    for(int i = 1 ; i <= m ; i ++)
    {
        int u , v, w;
        cin>>u>>v>>w;
        add(u,v,w);
        add(v,u,w);
    }
    dijkstra();
    ll ans =  1;
    for(int i = 1 ; i <= n ; i ++)
    {
        for(int j = head[i] ; j != -1 ; j = edge[j].next)
        {
            int v = edge[j].t , w = edge[j].w;
            if(dis[v] == dis[i] + w)
                dp[v] ++, dp[v] %= mod;
        }
    }
    for(int i = 1 ; i <= n ; i ++)
        if(dp[i] != 0)
            ans = (ans * dp[i])%mod;
    cout<<ans%mod<<endl;
}