Binary Search Guessing Game-CodePudding

I am trying to create a small program that uses binary search algorithm to have the computer itself guess a number given a set of arguments.

The arguments the function takes in are how many 'tries' it has to guess and the values that it can guess between (for example, 5 tries to guess the number in between 0 and 10).

When I run my code, it only seems to run my else: statement, regardless of the arguments I pass in.

I am missing something in my "if" statements but I am stumped and can't figure out what I have done incorrectly.

Thank you so much for your time and help!

import random

def guess_random_number_binary(tries, start, stop):
    
    rand_number = random.randint(start,stop)
    num_list = range(start,stop)

    lower_bound = start
    upper_bound = len(str(stop)) - 1
    
    while lower_bound <= upper_bound:
        pivot = (lower_bound   upper_bound) // 2
        pivot_value = num_list[pivot]
    
        if pivot_value == rand_number and tries > 0:
            print("Found it! "   str(rand_number))
            return pivot
        if pivot_value > rand_number and tries > 0:
            upper_bound = pivot - 1
            tries -= 1
            print ("incorrect guess"   str(tries)   " Remaining")
        else:
            lower_bound = pivot   1
            print("Out of tries")
            return


guess_random_number_binary(5, 0 ,10)

UPDATE:

import random

def guess_random_number_binary(tries, start, stop):
    
    rand_number = random.randint(start,stop)    
    num_list = []

    lower_bound = start
    upper_bound = stop
    
    num_list = range(start,stop 1)
     
    while lower_bound <= upper_bound:
                
        pivot = (lower_bound   upper_bound) // 2
        pivot_value = num_list[pivot]

        if tries > 0:
            if pivot_value == rand_number:
                print("Found it! "   str(rand_number))
                return pivot
            elif pivot_value > rand_number:
                upper_bound = pivot - 1
                tries -= 1
                print ("Guessed "   str(pivot)   " incorrectly \n"    str(tries)   " Tries remaining")
            elif pivot_value < rand_number:
                lower_bound = pivot   1
                tries -= 1
                print ("Guessed "   str(pivot)   " incorrectly \n"    str(tries)   " Tries remaining")
        else:
            print ("Ran out of tries!")
            break


guess_random_number_binary(5, 20 ,30)

I have been trying to debug and even if my new code is over simplified, I hope that it is at least headed in the right direction.

I believe the main issue stands with how I am creating "num_list" as pointed out by an answer below. Receiving an IndexError, which makes sense in theory. However, I cannot seem to find an alternative for creating that list.

Once again, thank you.

CodePudding user response：

You're resetting the value of pivot at the beginning of each loop, so

You passed in the value 10 for stop. So in the line upper_bound = len(str(stop)) - 1,

upper_bound = len(str(stop))-1 = len(str(10) = len ('10')-1 = 1.

Your while loop never runs, because lower_bound is never less than upper_bound.

You perhaps were at some point intending to do upper_bound = len(num_list)-1 and somehow wrote upper_bound = len(str(stop)) - 1 instead. However, even that would not have been correct; the length of range(start,stop) is stop-start, not stop-start 1 (range is not inclusive of stop). And using range in the first place is unnecessarily confusing and would not work for larger start values. For instance, suppose (start, stop) = (20, 30). Then pivot will be 25. But the range object will have only 10 elements, so num_range[pivot] will return an error.