[POJ 1101]The Game Bfs

题目大意

代码

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
#include <cstdlib>
using namespace std;

int w,h,mat[500][500],x1,y1,x2,y2,dir[4][2]={{1,0}/*down*/,{-1,0}/*up*/,{0,-1}/*left*/,{0,1}/*right*/},vis[500][500],cnt1=1,cnt2=1;
char t[500][500];

struct Holder{
int x,y,cnt;
}st,now,next,s,ed;

int Bfs(){
memset(vis,0,sizeof(vis));
queue<Holder> Q;
Q.push(s);vis[s.x][s.y]=1;
while(!Q.empty()){
now=Q.front();Q.pop();
if(now.x==ed.x&&now.y==ed.y&&now.cnt<ed.cnt){
ed.cnt=now.cnt;
}
for(int i=0;i<4;i++){
next.x=now.x+dir[i][0];
next.y=now.y+dir[i][1];
while(mat[next.x][next.y]==1&&next.x>=0&&next.x<=h+1&&next.y>=0&&next.y<=w+1&&vis[next.x][next.y]==0){
vis[next.x][next.y]=1;
next.cnt=now.cnt+1;
Q.push(next);
next.x+=dir[i][0];
next.y+=dir[i][1];
}
}
}
}

void Initialize(){
memset(mat,0,sizeof mat);
memset(vis,0,sizeof vis);
memset(t,0,sizeof(t));
}
int main(){
while(scanf("%d%d",&w,&h)!=EOF){
if(w==0&&h==0){
return 0;
}
Initialize();
for(int i=1;i<=h;++i){
cin.get();
for(int j=1;j<=w; ++j)
cin.get(t[i][j]);
}
for(int i=0;i<=h+1;i++){
for(int j=0;j<=w+1;j++){
if(t[i][j]=='X'){
mat[i][j]=10;
}else mat[i][j]=1;
}
}
cout<<"Board #"<<cnt1++<<":"<<endl;cnt2=1;
while(1){
scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
if(x1==0&&y1==0&&x2==0&&y2==0){
break;
}
s.x=y1;s.y=x1;ed.x=y2;ed.y=x2;
s.cnt=0;ed.cnt=1<<20;
int flag=0;
if(mat[y2][x2]==10){
mat[y2][x2]=1;
flag=1;
}
Bfs();
if(flag==1){
mat[y2][x2]=10;
}
if(ed.cnt!=1<<20){
cout<<"Pair "<<cnt2++<<": "<<ed.cnt<<" segments."<<endl;
}else{
cout<<"Pair "<<cnt2++<<": impossible."<<endl;
}
}
cout<<endl;
}
}