P1144 最短路计数

题面

https://www.luogu.org/problem/P1144

题解

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
const int mod=100003;
int n,m,dis[1050000],f[1050000];
bool vis[1050000];
vector <int> to[1050000];
queue<int> que;
int main(){
  int i,u,v,l;
  scanf("%d %d",&n,&m);
  for (i=1;i<=m;i++) {
    scanf("%d %d",&u,&v);
    to[u].push_back(v);
    to[v].push_back(u);
  }
  f[1]=1; dis[1]=0;
  memset(vis,0,sizeof(vis));
  vis[1]=true;
  que.push(1);
  while (!que.empty()) {
    u=que.front(); que.pop();
    l=to[u].size();
    for (i=0;i<l;i++) if (!vis[to[u][i]]) {
      vis[to[u][i]]=true;
      dis[to[u][i]]=dis[u]+1;
      f[to[u][i]]=f[u];
      que.push(to[u][i]);
    }
    else if (vis[to[u][i]] && dis[to[u][i]]==dis[u]+1) f[to[u][i]]=(f[to[u][i]]+f[u])%mod;
  }
  for (i=1;i<=n;i++) printf("%d
",f[i]);
}