Binary search
This technique uses a binary search to find a target integer in a RandomAccessFile. It is just concerned with integers.
This is the code:
//determines if a target number is in a RandomAccessFile using a binary search
//tracks the number of times it took to find that the number was/wasn't in the file
public static void binarySearch(){
Scanner input = new Scanner(System.in);
int target = 0; //the number being searched for
boolean targetFound = false; //indicates if the target is found
int searchCount = 0; //the number of times it took to find that the number was/wasn't in the file
System.out.print("Please enter the number you wish to search for: "); target = input.nextInt(); try{ RandomAccessFile raf = new RandomAccessFile("Project10.dat", "r"); long low = 0; long high = raf.length() - 1; int cur = 0; while(high >= low){ long mid = (low + high) / 2; raf.seek(mid); cur = raf.readInt(); System.out.println(cur); //for debugging searchCount++; if(target < cur){ high = mid - 4; } else if(target == cur){ targetFound = true; break; } else{ low = mid + 4; } } raf.close(); } catch(FileNotFoundException e){ e.printStackTrace(); } catch (IOException e){ e.printStackTrace(); } if(targetFound == true){ System.out.println("The number " + target + " is in the file. It took " + searchCount + " tries to discover this."); } else{ System.out.println("The number " + target + " is not in the file. It took " + searchCount + " tries to discover this."); }
}//end method binarySearch
I've tried everything, but I'm getting the wrong results. Because a raf comprises bytes and an integer contains four bytes, I figured I'd just decrease the high by four and increase the low by four, as described in this blog, where the identical operations were performed by one in a typical binary search. Apparently, this is not the case, and I'm still struggling to understand binary I/O in general. Help?
Answers
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