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You are absolutely right. That being said, sometimes it may be better to write code that exhibits explicitly its logic, here "summing the elements of the diagonal of a square matrix" and for this purpose using a 2-D array could be better here I guess.
But yes, when it comes to performances, storing data used only once is clearly ineffective.
In software engineering, algorithms get complex; part of being a good programmer is breaking down things into structured components and providing adequate documentation for your work, to both ensure you fully understand why what you did works and so others can better understand it during code review. Using an array for this is an incredibly sloppy thing to do, because there is no need for it and you would still need an algorithm to calculate the values in the array--you should not add layers of complexity to your code that have no benefit. The only reason to use an array for this type of thing would be if you knew there would be a future need to perform additional calculations on the same set of data. At my job, an attempt to use an array for something like this would be kicked back in a code review and never make it to release.
IMHO, I would preffer saying "it depends", if I had to reuse this code for some reason,it would be written as a function or a method, in this case the array would be provided as a parameter, therefore storing it is not an option, it is mandatory.
Another scenario would be calculating the difference as part of the processing, as you've mentioned.
But I defenitely agree that to solve this specific problem you don't need to store the information.
Well, you don't need to use the array, only the diagonals, as the task is very specific. Building on the idea that we might need to use the array later feels like a cop-out to explain bad coding. If you'd need to use the array values, you would be given a different task, not this one.
My solution used an array as the default template code (C++) provided such. Looking at various discussions of solutions to HR problems, it seems as if we're encouraged to remove the template code and just write our own solution. I'm sure it's mentioned somewhere.
If the task is to demonstrate algorithm skills then developers should be encouraged to start fresh. If however, the task is to demonstrate ability to process/manipulate an array or STL vector, then the best way would be to upgrade the HR testing system to just provide an interface (with the main hidden elsewhere). This would also mean coders don't have to deal with string streams for every single test. e.g.
classSolution:publicISolution{private:intevaluate(conststd::vector<std::vector<int>>&input){// implement solution here //}};
// focus on the intended problem, no need to think and waste times with string streams, cout & cin.
codingbat.com works like that, you just write the function - saves the hassle of writing basic stuff. On the other hand for people learning a language here, it helps a lot for these basics to burn in their memories.
Diagonal Difference
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You are absolutely right. That being said, sometimes it may be better to write code that exhibits explicitly its logic, here "summing the elements of the diagonal of a square matrix" and for this purpose using a 2-D array could be better here I guess.
But yes, when it comes to performances, storing data used only once is clearly ineffective.
In software engineering, algorithms get complex; part of being a good programmer is breaking down things into structured components and providing adequate documentation for your work, to both ensure you fully understand why what you did works and so others can better understand it during code review. Using an array for this is an incredibly sloppy thing to do, because there is no need for it and you would still need an algorithm to calculate the values in the array--you should not add layers of complexity to your code that have no benefit. The only reason to use an array for this type of thing would be if you knew there would be a future need to perform additional calculations on the same set of data. At my job, an attempt to use an array for something like this would be kicked back in a code review and never make it to release.
IMHO, I would preffer saying "it depends", if I had to reuse this code for some reason,it would be written as a function or a method, in this case the array would be provided as a parameter, therefore storing it is not an option, it is mandatory.
Another scenario would be calculating the difference as part of the processing, as you've mentioned.
But I defenitely agree that to solve this specific problem you don't need to store the information.
Well, you don't need to use the array, only the diagonals, as the task is very specific. Building on the idea that we might need to use the array later feels like a cop-out to explain bad coding. If you'd need to use the array values, you would be given a different task, not this one.
My solution used an array as the default template code (C++) provided such. Looking at various discussions of solutions to HR problems, it seems as if we're encouraged to remove the template code and just write our own solution. I'm sure it's mentioned somewhere.
If the task is to demonstrate algorithm skills then developers should be encouraged to start fresh. If however, the task is to demonstrate ability to process/manipulate an array or STL vector, then the best way would be to upgrade the HR testing system to just provide an interface (with the main hidden elsewhere). This would also mean coders don't have to deal with string streams for every single test. e.g.
// focus on the intended problem, no need to think and waste times with string streams, cout & cin.
Just my two cents.
codingbat.com works like that, you just write the function - saves the hassle of writing basic stuff. On the other hand for people learning a language here, it helps a lot for these basics to burn in their memories.