Simplistic way to represent tree-like data?-CodePudding

I have some JSON data that I want to match to a particular array of IDs. So for example, the JSON temperature: 80, weather: tornado can map to an array of IDs [15, 1, 82]. This array of IDs is completely arbitrary and something I will define myself for that particular input, it's simply meant to give recommendations based on conditions.

So while a temperature >= 80 in tornado conditions always maps to [15, 1, 82], the same temperature in cloudy conditions might be [1, 16, 28], and so on.

The issue is that there are a LOT of potential "branches". My program has 7 times of day, each of those time of day nodes has 7 potential temperature ranges, and each of those temperature range nodes have 15 possible weather events. So manually writing if statements for 735 combinations (if I did the math correctly) would be very unruly.

I have drawn a "decision tree" representing one path for demonstration purposes, above.

What are some recommended ways to represent this in code besides massively nested conditionals/case statements?

Thanks.

CodePudding user response：

No need for massive branching. It's easy enough to create a lookup table with the 735 possible entries. You said that you'll add the values yourself.

Create enums for each of your times of day, temperature ranges, and weather events. So your times of day are mapped from 0 to 6, your temperature ranges are mapped from 0 to 6, and your weather events are mapped from 0 to 14. You basically have a 3-dimensional array. And each entry in the array is a list of ID lists.

In C# it would look something like this:

List<List<int>>[][][] = LookupTable[7][7][15];

To populate the lookup table, write a program that generates JSON that you can include in your program. In pseudocode:

for (i = 0 to 6) {       // loop for time of day
  for (i = 0 to 6) {     // loop for temperature ranges
    for (i = 0 to 14) {  // loop for weather events
      // here, output JSON for the record
      // You'll probably want a comment with each record
      // to say which combination it's for.
      // The JSON here is basically just the list of
      // ID lists that you want to assign.
    }
  }
}

Perhaps you want to use that program to generate the JSON skeleton (i.e. one record for each [time-of-day, temperature, weather-event] combination), and then manually add the list of ID lists.

It's a little bit of preparation, but in the end your lookup is dead simple: convert the time-of-day, temperature, and weather event to their corresponding integer values, and look it up in the array. Just a few lines of code.

You could do something similar with a map or dictionary. You'd generate the JSON as above, but rather than load it into a three-dimensional array, load it into your dictionary with the key being the concatenation of the three dimensions. For example, a key would be:

"early morning,lukewarm,squall"

There are probably other lookup table solutions, as well. Those are the first two that I came up with. The point is that you have a whole lot of static data that's very amenable to indexed lookup. Take advantage of it.