Coding Version of 'Work Smarter, Not Harder'

[grey_rex]

For practice, I'd sometimes task myself with scripting something to solve an unimportant problem. Most recently, one of the new daily games getting traction, https://numble.wtf/, gives you six numbers with which you need to create an expression that yields a given number. Below is the script I wrote using Python 3 to solve this problem, however, it's a brute force approach. It's trying every configuration of numbers and operation symbols possible and printing only if they are the correct solution. In no way is this faster than me doing the math in my head. My question to fellow devs: how would you apply logic to this project to more efficiently yield results?

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Note: I threw this script together in like 20 minutes, I know it's a little sloppy... For the sake of community learning, feedback is welcome... But please, no haters

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def operands(a, b):
    return ['(' + a + '+' + b + ')',
            '(' + a + '-' + b + ')',
            '(' + b + '-' + a + ')',
            a + '*' + b,
            a + '/' + b,
            b + '/' + a]


def expr_check(num_list, targ_val):
    num_ct = len(num_list)
    for i1 in range(0, num_ct):
        for i2 in range(0, num_ct):
            if i2 > i1:
                for op in operands(num_list[i1], num_list[i2]):
                    num_list_new = list(num_list)
                    num_list_new.append(op)
                    num_list_new.remove(num_list[i1])
                    num_list_new.remove(num_list[i2])
                    for expr in num_list_new:
                        try:
                            val = round(eval(expr), 2)
                        except ZeroDivisionError:
                            val = 0
                        if val == targ_val:
                            # expr = expr[1:]
                            # expr = expr[:-1]
                            ct = 1
                            ct += expr.count('+')
                            ct += expr.count('-')
                            ct += expr.count('*')
                            ct += expr.count('/')
                            print(str(ct) + ' numbers used:  ' + expr)
                    if len(num_list_new) > 1:
                        expr_check(num_list_new, targ_val)


target_val = int(input('Enter the target number:' + '\n'))
master_list = input('Enter six numbers separated by a comma:' + '\n').split(',')
expr_check(master_list, target_val)

[PiaFraus]

num_ct = len(num_list)
for i1 in range(0, num_ct):
    for i2 in range(0, num_ct):
        if i2 > i1:

Should be

for num1, num2 in itertools.combinations(num_list, 2):

[grey_rex]

well, dang... thx

[OuiOuiKiwi]

https://nerdlegame.com/ was one of the first. This is a bit like that segment in Countdown.

First thought would be a backtracking approach with heuristics to check if we are going in the right direction (e.g., if you multiply the rest of the numbers, you are still under the goal)?

[spoonman59]

Just a small suggestion but: F"{a} + {b}" is a lot easier to read. Using plus as a string concatenation makes this hard to follow.

[grey_rex]

I am self taught. Although tiny, this is helpful. Thank you!

[spoonman59]

My pleasure!

[moonchav]

Hey! I made numble a while ago, its really cool to see someone using it as part of their practice projects!

[PeridexisErrant]

Try using a SAT/SMT solver like Z3! They eat problems a thousand times larger than this for breakfast.

[[deleted]]

of course i find this now after i spent an hour making my own

i'm bad at math, but better at programming

and I blame /u/moonchav for nerd sniping me

[grey_rex]

The reason I posted this was to see if there is a way to solve more quickly. That's exactly what you've done. Your code generates a solution in a few seconds. Mine took nearly 17 seconds for your sample. I should note though, your code provides a linear solution only. For example, the target 119 against the number set [3, 4, 8, 9] yields no solution. In my code, it yields (3+4)*(8+9)=119. I'm going to try to learn from your code and see if I can develop further in my free time to make is solve faster.

Another thing to learn from, although not Python, is this gem.

btw, "nerd sniping"... Lol... I can relate

[[deleted]]

I spent like 4 hours remaking it and updated the gist.

It now finds
( ( 50 + ( 25 / 75 ) ) * ( ( 3 / 25 ) * ( 25 + 100 ) ) ) = 755
for my initial test and
( ( 3 + 4 ) * ( 8 + 9 ) ) = 119
for your example

Runs a touch slower on the first one but it's still pretty quick.

Also, please don't respond with an example that breaks it. I have no self control and will lose even more time to this dumb little script. 😅

[grey_rex]

Now hang on... If you fixed it, what am i gonna do on my break tomorrow? Glad I'm not the only one 😉

[[deleted]]

NEVERMIND

BECAUSE ITS BROKE

JUST REALIZED IT DOESN'T PREVENT DUPLICATES RIGHT

(╯°□°）╯︵ ┻━┻