【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 = 100003;
const int maxn = 2000010;
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 = 0; i < e[now1].size(); i++)
        {
            int now2 = e[now1][i];
            if(!vis[now2])
            {
                vis[now2] = 1;
                dis[now2] = dis[now1]+1;
                q.push(now2);
            }
            if(dis[now2] == dis[now1]+1)
            {
                ans[now2] = (ans[now2] + ans[now1])%mod;
            }
        }
    }
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i = 1; i <= m; i++)
    {
        int u,v;
        scanf("%d%d",&u,&v);
        e[u].push_back(v);
        e[v].push_back(u);
    }
    int s = 1;
    dis[s] = 0;
    q.push(s);
    vis[s] = 1;
    ans[s] = 1;
    SPFA();
    for(int i = 1; i <= n; i++)
    printf("%d
",ans[i]);
}