poj 1475 Pushing Boxes(bfs)
来源:互联网 发布:西门子300plc编程软件 编辑:程序博客网 时间:2024/05/17 22:06
Pushing Boxes
Time Limit: 2000MS Memory Limit: 131072KTotal Submissions: 4846 Accepted: 1671 Special Judge
Description
Imagine you are standing inside a two-dimensional maze composed of square cells which may or may not be filled with rock. You can move north, south, east or west one cell at a step. These moves are called walks.
One of the empty cells contains a box which can be moved to an adjacent free cell by standing next to the box and then moving in the direction of the box. Such a move is called a push. The box cannot be moved in any other way than by pushing, which means that if you push it into a corner you can never get it out of the corner again.
One of the empty cells is marked as the target cell. Your job is to bring the box to the target cell by a sequence of walks and pushes. As the box is very heavy, you would like to minimize the number of pushes. Can you write a program that will work out the best such sequence?
One of the empty cells contains a box which can be moved to an adjacent free cell by standing next to the box and then moving in the direction of the box. Such a move is called a push. The box cannot be moved in any other way than by pushing, which means that if you push it into a corner you can never get it out of the corner again.
One of the empty cells is marked as the target cell. Your job is to bring the box to the target cell by a sequence of walks and pushes. As the box is very heavy, you would like to minimize the number of pushes. Can you write a program that will work out the best such sequence?
Input
The input contains the descriptions of several mazes. Each maze description starts with a line containing two integers r and c (both <= 20) representing the number of rows and columns of the maze.
Following this are r lines each containing c characters. Each character describes one cell of the maze. A cell full of rock is indicated by a `#' and an empty cell is represented by a `.'. Your starting position is symbolized by `S', the starting position of the box by `B' and the target cell by `T'.
Input is terminated by two zeroes for r and c.
Following this are r lines each containing c characters. Each character describes one cell of the maze. A cell full of rock is indicated by a `#' and an empty cell is represented by a `.'. Your starting position is symbolized by `S', the starting position of the box by `B' and the target cell by `T'.
Input is terminated by two zeroes for r and c.
Output
For each maze in the input, first print the number of the maze, as shown in the sample output. Then, if it is impossible to bring the box to the target cell, print ``Impossible.''.
Otherwise, output a sequence that minimizes the number of pushes. If there is more than one such sequence, choose the one that minimizes the number of total moves (walks and pushes). If there is still more than one such sequence, any one is acceptable.
Print the sequence as a string of the characters N, S, E, W, n, s, e and w where uppercase letters stand for pushes, lowercase letters stand for walks and the different letters stand for the directions north, south, east and west.
Output a single blank line after each test case.
Otherwise, output a sequence that minimizes the number of pushes. If there is more than one such sequence, choose the one that minimizes the number of total moves (walks and pushes). If there is still more than one such sequence, any one is acceptable.
Print the sequence as a string of the characters N, S, E, W, n, s, e and w where uppercase letters stand for pushes, lowercase letters stand for walks and the different letters stand for the directions north, south, east and west.
Output a single blank line after each test case.
Sample Input
1 7SB....T1 7SB..#.T7 11############T##......##.#.#..#####....B....##.######..##.....S...############8 4.....##..#...#...#.B.##S....###T0 0
Sample Output
Maze #1EEEEEMaze #2Impossible.Maze #3eennwwWWWWeeeeeesswwwwwwwnNNMaze #4swwwnnnnnneeesssSSS
#include <iostream>#include <stdio.h>#include <string.h>#include <math.h>#include <queue>#define INF 100000000using namespace std;int n,m;char map[22][22];bool vis[22][22][22][22]; //标记人和箱子的位置int dir[4][2]={{-1,0},{0,1},{1,0},{0,-1}};int father[1000*1000];char ans[1000*1000];struct node{ int x1,y1; int x2,y2; int step; //总的步数 int pnum; //push数 int id; bool operator <(const node &a)const { if(pnum!=a.pnum) return pnum>a.pnum; return step>a.step; }};node s,e;void dfs(int id) //递归输出路径{ if(father[id]!=-1) { dfs(father[id]); printf("%c",ans[id]); }}int bfs(){ node temp; priority_queue<node>q; s.step=0; s.pnum=0; s.id=0; memset(vis, false, sizeof(vis)); q.push(s); vis[s.x1][s.y1][s.x2][s.y2]=true; father[0]=-1; int id=1; while (!q.empty()) { s=q.top(); q.pop(); if(s.x2==e.x2 && s.y2==e.y2) return s.id; for (int i=0; i<4; i++) { temp=s; temp.x1+=dir[i][0]; temp.y1+=dir[i][1]; int x=temp.x1; int y=temp.y1; if(x<0 || x>=n || y<0 || y>=m || map[x][y]=='#') continue; if(x==temp.x2 && y==temp.y2) //遇到箱子,推箱子 { int xx=x+dir[i][0]; int yy=y+dir[i][1]; if(xx<0 || xx>=n || yy<0 || yy>=m || map[xx][yy]=='#') continue; if(!vis[x][y][xx][yy]) { vis[x][y][xx][yy]=true; father[id]=temp.id; temp.id=id; temp.x2=xx; temp.y2=yy; temp.step++; //总步数++ temp.pnum++; //推箱子次数++ q.push(temp); if(i==0) ans[id]='N'; if(i==1) ans[id]='E'; if(i==2) ans[id]='S'; if(i==3) ans[id]='W'; id++; } } else //没遇到箱子 { if(!vis[x][y][temp.x2][temp.y2]) { temp.step++; father[id]=temp.id; temp.id=id; if(i==0) ans[id]='n'; if(i==1) ans[id]='e'; if(i==2) ans[id]='s'; if(i==3) ans[id]='w'; id++; vis[x][y][temp.x2][temp.y2]=true; q.push(temp); } } } } return -1;}int main(){ int cnt=0; while (scanf("%d%d",&n,&m) && (n+m)) { for (int i=0; i<n; i++) { scanf("%s",map[i]); for (int j=0; j<m; j++) { if(map[i][j]=='B') { s.x2=i; s.y2=j; } else if(map[i][j]=='T') { e.x2=i; e.y2=j; } else if(map[i][j]=='S') { s.x1=i; s.y1=j; } if(map[i][j]!='#') map[i][j]='.'; } } int id=bfs(); printf("Maze #%d\n",++cnt); if (id==-1) printf("Impossible."); else dfs(id); printf("\n\n"); } return 0;}
0 0
- Pushing Boxes (poj 1475 嵌套bfs)
- poj 1475 Pushing Boxes(bfs)
- POJ 1475 Pushing Boxes(BFS)
- POJ 1475 Pushing Boxes(BFS)
- POJ 1475 Pushing Boxes(嵌套BFS)
- POJ-1475-Pushing Boxes(BFS)
- poj 1475 Pushing Boxes(推箱子游戏,bfs+bfs)
- POJ 1475 Pushing Boxes 搜索- 两重BFS
- POJ 1475 Pushing Boxes 嵌套BFS -
- POJ 1475 Pushing Boxes 【A*bfs套bfs】
- poj 1475 Pushing Boxes
- (poj 1475) Pushing Boxes
- POJ - 1475 Pushing Boxes
- POJ 1475 Pushing Boxes
- poj 1475 Pushing Boxes
- POJ 1475 Pushing Boxes
- poj 1475 Pushing Boxes
- POJ 1475:Pushing Boxes
- noip2001 装箱问题 (01背包)
- ACM 正负大数的读入外挂模板+单调队列模板
- 数据结构之队列
- Billboard 线段树更新叶子节点
- 面试题20顺时针打印矩阵
- poj 1475 Pushing Boxes(bfs)
- Dungeon Master
- Android:学习笔记(一)
- Excel Sheet Column Number
- Unity3D汽车物理引擎的安卓重力感应适配
- Android UI之QuickContactBasge
- LeetCode(29)Divide Two Integers
- 【POJ2236】【Wireless Network】【注意初始化-1】【并查集】【连通性】
- 最小生成树+Hdu4786