题目地址:http://poj.org/problem?id=1729
本来想用string保存路程 后来发现太慢了
优先队列要以一条路中最近的距离排序
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<cmath>
#include<cstring>
using namespace std;
const int maxn=30+5;
const double INF=999999999;
char G[maxn][maxn];
int vis[maxn][maxn][maxn][maxn];
int n;
struct Point{
int x,y;
Point(int x=0,int y=0):x(x),y(y){}
bool operator == (const Point& p){
return x==p.x&&y==p.y;
}
bool operator != (const Point& p){
return !(*this==p);
}
};
int inline Dist(Point a,Point b){
return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
}
struct Node{
Point Jack,Jill; int dist,pre,id; //dist 保存此路中相聚最近的距离
int d1,d2;
Node(Point a=Point(0,0),Point b=Point(0,0),int pre=-1,int id=0,int p1='*',int p2='*',int dist=INF):id(id),Jack(a),Jill(b),d1(p1),d2(p2),pre(pre),dist(dist){}
bool operator < (const Node& n) const {
return dist<n.dist;
}
}node[1000000+10];
const int dx[4]={-1,0,1,0};
const int dy[4]={0,-1,0,1};
const char d[5]="NWSE";
Point move(Point p,int i) {
return Point(p.x+dx[i],p.y+dy[i]);
}
bool inside(Point p){
return p.x>=1&&p.x<=n&&p.y>=1&&p.y<=n;
}
int Min=INF;
int cnt;
void BFS(Point s1,Point s2,Point t1,Point t2)
{
memset(vis,-1,sizeof(vis));
priority_queue<Node> PQ;
Node s(s1,s2,-1,0,'*','*',Dist(s1,s2));
PQ.push(s);
cnt=0; node[cnt++]=s;
vis[s1.x][s1.y][s2.x][s2.y]=Dist(s1,s2);
while(!PQ.empty())
{
Node u=PQ.top(); PQ.pop();
if(u.Jack==t1&&u.Jill==t2){
printf("%.2f\n",sqrt(u.dist));
string str1,str2;
Node p=u;
while(p.pre!=-1)
{
if(p.d1!='*') str1+=p.d1;
if(p.d2!='*') str2+=p.d2;
p=node[p.pre];
}
reverse(str1.begin(),str1.end());
reverse(str2.begin(),str2.end());
cout<<str1<<endl;
cout<<str2<<endl;
return;
}
for(int i=0;i<4;i++)
{
Point ns1=move(u.Jack,i); int d1=d[i];
if(u.Jack==t1) ns1=u.Jack,d1='*';
if(!inside(ns1)||G[ns1.x][ns1.y]=='#'||G[ns1.x][ns1.y]=='*') continue;
for(int j=0;j<4;j++)
{
Point ns2=move(u.Jill,j); int d2=d[j];
if(u.Jill==t2) ns2=u.Jill,d2='*';
if(!inside(ns2)||G[ns2.x][ns2.y]=='*'||G[ns2.x][ns2.y]=='$') continue;
int dis=min(u.dist,Dist(ns1,ns2));
Node v(ns1,ns2,u.id,cnt,d1,d2,dis);
int& vt=vis[ns1.x][ns1.y][ns2.x][ns2.y];
if(vt==-1||vt<dis) {
vt=dis;
PQ.push(v); node[cnt++]=v;
}
}
}
}
}
int main()
{
while(cin>>n&&n)
{
Point s1,s2,t1,t2;
for(int i=1;i<=n;i++)
for(int j=1;j<=n;j++)
{
cin>>G[i][j];
if(G[i][j]=='H') s1=Point(i,j),G[i][j]='$';
else if(G[i][j]=='h') s2=Point(i,j),G[i][j]='#';
else if(G[i][j]=='S') t1=Point(i,j),G[i][j]='$';
else if(G[i][j]=='s') t2=Point(i,j),G[i][j]='#';
}
BFS(s1,s2,t1,t2);
}
return 0;
}