HDU 1010 Tempter of the Bone DFS(奇偶剪枝优化)
需要剪枝否则会超时,然后就是基本的深搜了
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include<cstdio> #include<stdio.h> #include<cstdlib> #include<cmath> #include<iostream> #include<algorithm> #include<cstring> #include<vector> #include<queue> #define INF 0x3f3f3f3f #define MAX 1005 using namespace std; char Map[MAX][MAX]; int time,n,m,sx,sy,ex,ey,v[4][2]={{1,0},{0,1},{-1,0},{0,-1}},ok; bool check(int x,int y) { if(x>=0 && x<n && y>=0 && y<m && Map[x][y]!='X') return true; return false; } void DFS(int x,int y,int step) { if(x==ex && y==ey && step==time) { ok=1; return; } else if(step >= time || ok) return; for(int i=0;i<4;i++) { int new_x=x+v[i][0]; int new_y=y+v[i][1]; if(check(new_x,new_y)) { Map[new_x][new_y]='X'; DFS(new_x,new_y,step+1); Map[new_x][new_y]='.'; } } } int main() { while(scanf("%d%d%d",&n,&m,&time),n+m+time) { ok=0; for(int i=0;i<n;i++) scanf("%s",Map[i]); for(int i=0;i<n;i++) { for(int j=0;j<m;j++) { if(Map[i][j]=='S') { sx=i; sy=j; } if(Map[i][j]=='D') { ex=i; ey=j; } } } int k1=abs(sx-ex); int k2=abs(sy-ey); if((time-(k1+k2))%2)//奇偶剪纸 { printf("NO\n"); continue; } if(sx==ex && sy==ey) { printf("YES\n"); continue; } Map[sx][sy]='X'; DFS(sx,sy,0); if(ok) printf("YES\n"); else printf("NO\n"); } return 0; }