【luogu P1144 最短路计数】 题解

题目链接：https://www.luogu.org/problemnew/show/P1144

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <queue>
 #include <vector>
 using namespace std;
 const int mod = ;
 const int maxn = ;
 const int inf = 0x7fffffff;
 int n, m, dis[maxn], ans[maxn];
 bool vis[maxn];
 queue<int>q;
 vector<int>e[maxn];
 int SPFA()
 {
     while(!q.empty())
     {
         int now1 = q.front();
         q.pop();
         for(int i = ; i < e[now1].size(); i++)
         {
             int now2 = e[now1][i];
             if(!vis[now2])
             {
                 vis[now2] = ;
                 dis[now2] = dis[now1]+;
                 q.push(now2);
             }
             if(dis[now2] == dis[now1]+)
             {
                 ans[now2] = (ans[now2] + ans[now1])%mod;
             }
         }
     }
 }
 int main()
 {
     scanf("%d%d",&n,&m);
     for(int i = ; i <= m; i++)
     {
         int u,v;
         scanf("%d%d",&u,&v);
         e[u].push_back(v);
         e[v].push_back(u);
     }
     int s = ;
     dis[s] = ;
     q.push(s);
     vis[s] = ;
     ans[s] = ;
     SPFA();
     for(int i = ; i <= n; i++)
     printf("%d\n",ans[i]);
 }