【模板】最短路计数

洛谷 1144

dijkstra+手写堆

#include<cstdio>
#include<algorithm>
#define N 2000010
#define Mod 100003
#define rg register
using namespace std;
int n,m,tot,dis[N],last[N],cnt[N],pos[N];
struct edge{
	int to,pre,dis;
}e[N];
struct heap{
	int poi,dis;
}h[N];
inline int read(){
	int k=0,f=1; char c=getchar();
	while(c<‘0‘||c>‘9‘)c==‘-‘&&(f=-1),c=getchar();
	while(‘0‘<=c&&c<=‘9‘)k=k*10+c-‘0‘,c=getchar();
	return k*f;
}
inline void add(int x,int y){
	e[++tot]=(edge){y,last[x],1}; last[x]=tot;
}
inline void MOD(int &x){
	if(x>=Mod) x-=Mod;
}
inline void up(int x){
	int fa;
	while((fa=x>>1)&&h[fa].dis>h[x].dis){
		swap(h[x],h[fa]); swap(pos[h[x].poi],pos[h[fa].poi]);
		x=fa;
	}
}
inline void down(int x){
	int son;
	while((son=(x<<1))<=tot){
		if(son<tot&&h[son].dis>h[son+1].dis) son++;
		if(h[son].dis<h[x].dis){
			swap(h[x],h[son]); swap(pos[h[x].poi],pos[h[son].poi]);
			x=son;
		}
		else return;
	}
}
void dijkstra(int x){
	h[tot=pos[x]=cnt[x]=1]=(heap){1,dis[x]=0};
	while(tot){
		int now=h[1].poi; h[1]=h[tot--]; if(tot) down(1);
		for(rg int i=last[now],to;i;i=e[i].pre)
		if(dis[to=e[i].to]>=dis[now]+e[i].dis){
			if(dis[to]==dis[now]+e[i].dis) cnt[to]+=cnt[now],MOD(cnt[to]);
			else{
				dis[to]=dis[now]+e[i].dis; cnt[to]=cnt[now];
				if(!pos[to]) h[pos[to]=++tot]=(heap){to,dis[to]};
				else h[pos[to]].dis=dis[to];
				up(pos[to]);
			}
		}
	}
}
int main(){
//	freopen("testdata.in","r",stdin);
//	freopen("my.out","w",stdout);
	n=read(); m=read();
	for(rg int i=1;i<=n;i++) dis[i]=0X7f7f7f7f;
	for(rg int i=1,u,v;i<=m;i++){
		u=read(),v=read();
		//if(u==v) continue;
		add(u,v); add(v,u);
	}
	dijkstra(1);
	for(rg int i=1;i<=n;i++) printf("%d\n",cnt[i]);
	//puts(""); for(rg int i=1;i<=n;i++) printf("%d ",dis[i]);
	return 0;
}

原文地址：https://www.cnblogs.com/DriverLao/p/8548923.html