深度优先搜索篇Tempter of the Bone
Tempter of the Bone
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 40933 Accepted Submission(s): 11070
The maze was a rectangle with sizes N by M. There was a door in the maze. At the beginning, the door was closed and it would open at the T-th second for a short period of time (less than 1 second). Therefore the doggie had to arrive at the door on exactly the T-th second. In every second, he could move one block to one of the upper, lower, left and right neighboring blocks. Once he entered a block, the ground of this block would start to sink and disappear in the next second. He could not stay at one block for more than one second, nor could he move into a visited block. Can the poor doggie survive? Please help him.
'X': a block of wall, which the doggie cannot enter;
'S': the start point of the doggie;
'D': the Door; or
'.': an empty block.
The input is terminated with three 0's. This test case is not to be processed.
4 4 5 S.X. ..X. ..XD .... 3 4 5 S.X. ..X. ...D 0 0 0
NO YES
#include<iostream>
using namespace std;
char p[8][8];
int biaoji;
int c[4]={0,1,0,-1};
int d[4]={-1,0,1,0};
int x1,y1,x2,y2,m,n,T;
int lmx(int x)
{
if(x>=0) return x;
else return -x;
}
void dfs(int x,int y,int t)
{
int i,xx,yy;
if(t==T&&x==x2&&y==y2)
{
biaoji=1;
}
if(biaoji==1) return;//此语句与上面一句必须分开否则超时暂时没想明白
if((lmx(x2-x)+lmx(y2-y))%2!=(T-t)%2||t>T) return;//重要的奇偶剪枝剩余的时间和剩下的步数就行必须相同
for(i=0;i<4;i++)
{
xx=x+c[i];
yy=y+d[i];
if(p[xx][yy]!='X'&&xx>=0&&xx<m&&yy>=0&&y<n)
{
p[xx][yy]='X';
dfs(xx,yy,t+1);
p[xx][yy]='.';
}
}
}
int main()
{
int i,j,cnt;
while(cin>>m>>n>>T)
{
if(m==0&&n==0&&T==0) break;
cnt=0;
for(i=0;i<m;i++)
{
for(j=0;j<n;j++)
{
cin>>p[i][j];
if(p[i][j]=='S') {x1=i;y1=j;}
if(p[i][j]=='D') {x2=i;y2=j;cnt++;}
if(p[i][j]=='.') cnt++;
}
}
if(cnt<T||lmx(x2-x1)+lmx(y2-y1)>T) cout<<"NO"<<endl;//剪枝判断是否有搜索的必要加上此句快乐三百多ms
else
{
p[x1][y1]='X';
biaoji=0;
dfs(x1,y1,0);
if(biaoji==1) cout<<"YES"<<endl;
else cout<<"NO"<<endl;
}
}
return 0;
}