Number countdown game

There are multiple ways to solve this. The smallest solution requires just four numbers:. For 26 years, this host role was performed by the talented Carol Vorderman. Are all problems solvable for a perfect score? Does there exist a three digit number that is not achievable by any combination of digits? If not, what is the hardest number to achieve? This was a fun piece of code to write. I elected to use a brute-force approach. There are 13, distinct ways of picking the numbers following the rules.

Then, for each of these distinct subsets, the number of distinct ways these numbers can be arranged in order was determined. The most obvious way to process these was to use Reverse Polish Notation to store the calculation postfix as opposed to the more traditional infix. A trap that needs to be avoided is the ordering the operators should be applied. In RPN notation these distinctions are obvious See table. Calculating all possible solutions is easy using RPN by permuting the order operators and operands within the constraints of a stack, so some combination as not possible; you can't operate on numbers if there are none in the stack!

An added benefit of using RPN is that, at the end of any operation you can check the stack and that will give you a possible intermediate solution remember not all numbers need to be used for a valid solution. This is not a valid answer, as it is less than a hundred the lowest possible target. However the next operation is multiplication by 5. This gives a result of , which is valid. There are some obvious optimisations that can be made in the algorithm plus a couple of things to watch out for :.

There is no benefit in multiply by 1 at any stage. This just makes a longer solution. If at any time the intermediate solution becomes negative, we can instantly bail on that solution.

You need to make sure you catch any potential divide by zero calculation that might happen as you test for possible solutions. It's very tempting to think about using 16 bit Integers to store intermediate but this is wrong for a couple of reasons. This would cause an overflow. The most convoluted I've heard about in the history of the show is this one for , followed closely by from an Australian version of the show. Pretty impressive! I find it easier to interpret infix rather than postfix equations, so I wrote a function to convert these back and insert the appropriate parenthesis after the calculations were over.

The 13, possible combinations that the tiles can be selected can be combined to make 10,, distinct solutions of tiles and target numbers.

If you were unlucky enough to draw these numbers there is nothing you could do. Even the lowest target of is more than 10 away from this, so no score is possible. See System Requirements. Available on Mobile device. Description Play the famous Countdown numbers game - complete with solutions.

Show More. What's new in this version Added a feedback option. Published by GUI Innovations. Developed by GUI Innovations. Approximate size 1. Age rating For all ages. This app can Access your Internet connection and act as a server.

Permissions info. Installation Get this app while signed in to your Microsoft account and install on up to ten Windows 10 devices. This product needs to be installed on your internal hard drive.

Bluey-green, white and transparent squares with a few odd bits of shapes around the perimeter. But, how many squares are there of each type in the complete circle? Study the picture and make an estimate. Here is a chance to play a version of the classic Countdown Game. The challenge is to use the numbers available and the four standard operations addition, subtraction, multiplication and division to hit the target.

Start by choosing any six cards. The top row always contains the numbers 25, 50, 75 and , and the bottom row contains the numbers 1 to