bzoj2200: [Usaco2011 Jan]道路和航线

先忽略航线,求出图中所有连通块,再用航线拓扑排序求出每个连通块的优先级

然后dijkstra时优先处理优先级高的块里的点就行了

ps:这题SPFA会TLE

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <queue>
#define N 25003
#define M 150004

using namespace std;
inline int read(){
	int ret=0;char ch=getchar();
	bool flag=0;
	while (ch<'0' || ch>'9'){
		flag=ch=='-';
		ch=getchar();
	}
	while ('0'<=ch && ch<='9'){
		ret=ret*10-48+ch;
		ch=getchar();
	}
	return flag?-ret:ret;
}

struct edge{
	int adj,next,len;
	edge(){}
	edge(int _adj,int _next,int _len):adj(_adj),next(_next),len(_len){}
} e[M];
int n,g[N],m,di[N];
void AddEdge(int u,int v,int w){
	e[++m]=edge(v,g[u],w);g[u]=m;
}

int col[N],cnt;
int q[N],qh,qt;
int a[N],start[N];
int degree[N];
int level[N];
void bfs(){
	qh=qt=0;
	memset(col,0,sizeof(col));
	for (int i=1;i<=n;++i)if (!col[i]){
		q[++qt]=i;
		col[i]=++cnt;
		start[cnt]=qt;
		while (qh<qt){
			int u=q[++qh];
			for (int i=di[u];i;i=e[i].next){
				int v=e[i].adj;
				if (col[v]) continue;
				col[v]=cnt;
				q[++qt]=v;
			}
		}
	}
	start[cnt+1]=qt+1;
	for (int i=1;i<=qt;++i) a[i]=q[i];
	memset(degree,0,sizeof(degree));
	for (int j=1;j<=n;++j)
		for (int i=g[j];i!=di[j];i=e[i].next){
			int v=e[i].adj;
			++degree[col[v]];
		}
	qh=qt=0;
	for (int i=1;i<=cnt;++i)
		if (!degree[i]) q[++qt]=i;
	int now=0;
	while (qh<qt){
		int u=q[++qh];
		level[u]=++now;
		for (int j=start[u];j<start[u+1];++j)
			for (int i=g[a[j]];i!=di[a[j]];i=e[i].next){
				int v=e[i].adj;
				if (!--degree[col[v]]) q[++qt]=col[v];
			}
	}
}


struct HeapNode{
	int pos,value;
	HeapNode(){}
	HeapNode(int _pos,int _value):pos(_pos),value(_value){}
};
inline bool operator >(const HeapNode &x,const HeapNode &y){
	return (level[col[x.pos]]>level[col[y.pos]]||level[col[x.pos]]==level[col[y.pos]]&&x.value>y.value);
}
priority_queue<HeapNode,vector<HeapNode> ,greater<HeapNode> > h;

int mind[N];
bool flag[N];
void dijkstra(int _s){
	memset(mind,127,sizeof(mind));
	memset(flag,0,sizeof(flag));
	while (!h.empty()) h.pop();
	h.push(HeapNode(_s,mind[_s]=0));
	while (!h.empty()){
		int u=h.top().pos;
		flag[u]=1;
		h.pop();
		for (int i=g[u];i;i=e[i].next){
			int v=e[i].adj;
			if (mind[v]>mind[u]+e[i].len){
				mind[v]=mind[u]+e[i].len;
				h.push(HeapNode(v,mind[v]));
			}
		}
		while (!h.empty()&&flag[h.top().pos]) h.pop();
	}
}


int main(){
	n=read();int m0=read(),m1=read(),s=read();
	memset(g,0,sizeof(g));m=1;
	while (m0--){
		int u=read(),v=read(),w=read();
		AddEdge(u,v,w);
		AddEdge(v,u,w);
	}
	for (int i=1;i<=n;++i) di[i]=g[i];
	while (m1--){
		int u=read(),v=read(),w=read();
		AddEdge(u,v,w);
	}
	bfs();
	dijkstra(s);
	for (int i=1;i<=n;++i)
		if (mind[i]>(1<<30)) puts("NO PATH");
		else printf("%d\n",mind[i]);
	return 0;
}

  

posted @ 2016-01-18 14:49  wangyurzee  阅读(274)  评论(0编辑  收藏  举报