COP 3530 HW6 - Solutions

Transcription

1 a) COP 3530 HW6 - Solutions package datastructures; import java.util.vector; public class RatInMaze int [][] maze_; int width_; int height_; ArrayStack stack_; ArrayQueue queue_; int traveled_; int pathlength_; private boolean isvalid(int x,int y) if((x < 0) (x >= width_)) if((y < 0) (y >= height_)) if(maze_[y][x] > 0) return true; private boolean search(int fromx,int fromy,int tox,int toy,boolean smart) traveled_ = 0; pathlength_ = 0; if(!isvalid(fromx,fromy)) System.out.println("Starting point is not inside the maze!"); if(!isvalid(tox,toy)) System.out.println("Ending point is not inside the maze!"); push(2,fromx,fromy); while(!isempty()) int pos = (Integer)pop(); traveled_++; int x = pos%width_; int y = pos/width_; if((x == tox)&&(y == toy)) if(!smart)

2 //Not a smart rat? //A smart rat! int dx = x - tox; int dy = y - toy; if(dx == 0) if(dy < 0) if(dy < 0) if(dy == 0) if(dx <= 0) if(dx <= 0)

3 if( dx < 0 ) if( dx > 0 ) if( dy < 0 ) if( dy > 0 ) if( dx < 0 ) if( dx > 0 ) if( dy < 0 ) if( dy > 0 ) // print(true); if(isvalid(tox,toy)) //Trace back int nx = tox; int ny = toy; while((nx!= fromx) (ny!= fromy)) int direction = maze_[ny][nx]; maze_[ny][nx] = 2; if(direction == 3) nx--; if(direction == 4) nx++; if(direction == 5) ny--; if(direction == 6) ny++; pathlength_++; return true; private Object pop() return stack_.pop();

4 return queue_.remove(); private void push(int d,int x,int y) int nx = x; int ny = y; switch(d) case 3: nx++; case 4: nx--; case 5: ny++; case 6: ny--; default: if(!isvalid(nx,ny)) return; maze_[ny][nx] = d; stack_.push(nx + ny* width_); queue_.put(nx + ny* width_); private boolean isempty() return stack_.empty(); return queue_.isempty(); public void load(vector<string> maze) height_ = maze.size(); if(height_ == 0) return;

5 width_ = maze.get(0).length(); if( width_ == 0 ) return; maze_= new int[height_][width_]; for(int i=0; i< height_; i++) for( int j=0 ; j <width_ ; j++ ) maze_[i][j] = maze.get(i).charat(j) - '0'; public void print(boolean found) String line = ""; String output = ""; output = "I"; output = "We"; if (found) for (int i = 0; i < height_; i++) line = ""; for (int j = 0; j < width_; j++) if((maze_[i][j] == 1) (maze_[i][j] == 2)) line += maze_[i][j]; line += 0; System.out.println(line); output += "'ve traveled through " + traveled_ + "square(s). The path contains " + pathlength_ + "square(s)"; System.out.println(output); System.out.println("I cannot get there."); public boolean searchstack(int fromx,int fromy,int tox,int toy) stack_= new ArrayStack(); queue_ = null; return search(fromx,fromy,tox, toy,false); public boolean searchstacksmart(int fromx,int fromy,int tox,int toy) stack_= new ArrayStack(); queue_ = null;

6 return search(fromx,fromy,tox, toy,true); public boolean searchqueue(int fromx,int fromy,int tox,int toy) stack_= null; queue_ = new ArrayQueue(); return search(fromx,fromy,tox, toy,false); // Please use the test code as follows. public static void main(string[] args) RatInMaze rim = new RatInMaze(); Vector <String> maze = new Vector<String>(); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); maze.add(" "); rim.print(rim.searchqueue(-1,1,10,10)); rim.print(rim.searchstack(0,0,41,1)); int fromx = 0; int fromy = 7; int tox = 14; int toy = 6; System.out.println("A rat is searching:"); rim.print(rim.searchstack(fromx,fromy,tox,toy)); System.out.println("Multiple rats are searching:"); rim.print(rim.searchqueue(fromx,fromy,tox,toy)); System.out.println("A smart rat is searching:"); rim.print(rim.searchstacksmart(fromx,fromy,tox,toy));

7 Output: A rat is searching: I've traveled through 78square(s). The path contains 45square(s) Multiple rats are searching: We've traveled through 134square(s). The path contains 39square(s) A smart rat is searching: I've traveled through 45square(s). The path contains 41square(s) d) The stack search rat had the longest path and number of squares traveled, the smart rat had the least number of spaces traveled but the second best path, and the queue rats had the best path length but the worst number of spots traveled. The choice of which method to use depends on what results the user wants; the queue method is the best method of finding the shortest path, but if the number of spaces traveled is to be minimized, the smart rat is the better choice.