[題解]luogu_P1144最短路計數

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
const int maxn=1000010;
const int maxm=2000010;
const int mod=100003;
int n,m;
int head[maxn],cnt;
struct node{
    int v,nxt;
}e[maxn*2];
void add(int u,int v){
    e[++cnt].v=v;e[cnt].nxt=head[u];head[u]=cnt;
}
queue<int>q;
int d[maxn],v[maxn],c[maxn];
void spfa(){
    d[1]=0;v[1]=1;q.push(1);
    c[1]=1;//初值 
    while(!q.empty()){
        int x=q.front();q.pop();v[x]=0;
        for(int i=head[x];i;i=e[i].nxt){
            int y=e[i].v;
            if(d[y]>d[x]+1){
                d[y]=d[x]+1;
                c[y]=c[x];//覆蓋 
                if(!v[y])q.push(y),v[y]=1;
            }
            else if(d[y]==d[x]+1)c[y]+=c[x],c[y]%=mod;//相等就合併 
        }
    }
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1,x,y;i<=m;i++){
        scanf("%d%d",&x,&y);
        add(x,y);add(y,x);
    }
    memset(d,0x3f,sizeof(d));
    spfa();
    for(int i=1;i<=n;i++)printf("%d\n",c[i]);
}