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AI-Based Problem Solving


Java is well-suited the programming discipline of artificial intelligence. Java's string-handling capabilities and Stack class make it easy to handle many types of AI-based code. If you would like to learn more about using Java to solve AI problems, keep reading. This article is excerpted from chapter ten of The Art of Java, written by Herbert Schildt (McGraw-Hill/Osborne, 2004; ISBN: 0072229713).

Author Info:
By: McGraw-Hill/Osborne
Rating: 4 stars4 stars4 stars4 stars4 stars / 30
June 02, 2005
TABLE OF CONTENTS:
  1. · AI-Based Problem Solving
  2. · Search Techniques
  3. · The Depth-First Search
  4. · An Analysis of the Depth-First Search
  5. · The Hill-Climbing Search
  6. · An Analysis of Hill Climbing
  7. · Node Removal
  8. · Finding the “Optimal” Solution
  9. · Back to the Lost Keys

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AI-Based Problem Solving - Back to the Lost Keys
(Page 9 of 9 )

To conclude this chapter on problem solving, it seems only fitting to provide a Java program that finds the lost car keys described in the first example. The accompanying code employs the same techniques used in the problem of finding a route between two cities, so the program is presented without further explanation.

// Find the lost keys!
import java.util.*;
import java.io.*;
// Room information.
class RoomInfo {
  String from;
  String to;
  boolean skip;
 
RoomInfo(String f, String t) {
    from = f;
    to = t;
    skip = false;
 
}
}
class Keys {
  final int MAX = 100;
 
// This array holds the room information.
  RoomInfo room[] = new RoomInfo[MAX];
 
int numRooms = 0; // number of rooms
 
Stack btStack = new Stack(); // backtrack stack
  public static void main(String args[])
 
{
    String to, from;
    Keys ob = new Keys();
   
ob.setup();
   
from = "front_door";
    to = "keys";
   
ob.iskeys(from, to);
   
if(ob.btStack.size() != 0)
      ob.route(to);
  }
  // Initialize the room database.
  void setup()
  {
   
addRoom("front_door", "lr");
   
addRoom("lr", "bath");
   
addRoom("lr", "hall");
   
addRoom("hall", "bd1");
   
addRoom("hall", "bd2");
   
addRoom("hall", "mb");
   
addRoom("lr", "kitchen");
   
addRoom("kitchen", "keys");
  }
 
// Put rooms into the database.
  void addRoom(String from, String to)
  {
   
if(numRooms < MAX) {
     
room[numRooms] = new RoomInfo(from, to);
     
numRooms++;
   
}
   
else System.out.println("Room database full.\n");
  }
 
// Show the route.
  void route(String to)
  {
   
Stack rev = new Stack();
   
RoomInfo r;
   
int num = btStack.size();
   
// Reverse the stack to display path.
    for(int i=0; i < num; i++)
      rev.push(btStack.pop());
   
for(int i=0; i < num; i++) {
     
r = (RoomInfo) rev.pop();
     
System.out.print(r.from + " to ");
    }
   
System.out.println(to);
  }
 
/* If there is a path between from and to,
     return true, otherwise return false. */
  boolean match(String from, String to)
  {
    for(int i=numRooms-1; i > -1; i--) {
     
if(room[i].from.equals(from) &&
        room[i].to.equals(to) &&
        !room[i].skip)
     
{
        room[i].skip = true; // prevent reuse
        return true;
     
}
    }
   
return false; // not found
  }
 
// Given from, find any path.
  RoomInfo find(String from)
  {
   
for(int i=0; i < numRooms; i++) {
      if(room[i].from.equals(from) &&
        !room[i].skip)
      {
        RoomInfo r = new RoomInfo(room[i].from,
                           room[i].to);
        room[i].skip = true; // prevent reuse
       
return r;
     
}
    }
    return null;
 
}
  // Determine if there is a path between from and to.
  void iskeys(String from, String to)
  {
   
int dist;
    RoomInfo r;
 
// See if at destination.
 
if(match(from, to)) {
    btStack.push(new RoomInfo(from, to));
    return;
 
}
    // Try another connection.
    r = find(from);
    if(r != null) {
      
btStack.push(new RoomInfo(from, to));
      
iskeys(r.to, to);
    }
    else if(btStack.size() > 0) {
      
// Backtrack and try another connection.
      r = (RoomInfo) btStack.pop();
      iskeys(r.from, r.to);
    
}
  }
}


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