Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>When implementing a recursive function, you need to think about two cases: the base case and the recursive case.</p> <p>In the base case, the function doesn't call itself recursively. It may do some work in this case, or it may do nothing because all the work has already been done.</p> <p>In the recursive case, the function does a little bit of work to get itself closer to the goal, then calls itself recursively to get the rest of the work done.</p> <p>Here's a way to break down your problem for a recursive function.</p> <p>In the recursive case, the “little bit of work” is setting the sign of one number in the list to positive, and <strong>also</strong> to set the sign of that number to negative. We need to recurse after both assignments, because we need to generate combinations for each sign.</p> <p>In the base case, all of the numbers have had their signs set, so we just print the list of numbers.</p> <p>In Python, for example, we could start by setting up the function to take a list of numbers, and the index of the next number needing its sign set. To start, the next number is the first number in the list, at index 0:</p> <pre><code>def allSignCombinations(numbers, nextNumberIndex=0): </code></pre> <p>The base case happens when <code>nextNumberIndex</code> is equal to <code>len(numbers)</code>, meaning there are no numbers left needing their signs set:</p> <pre><code> if nextNumberIndex == len(numbers): print numbers </code></pre> <p>Otherwise, we do that “little bit of work”. We set the sign of the next number to both positive and negative, and we recurse for each sign. When we recurse, we tell the next call to work starting at the next number in the list, if there is one:</p> <pre><code> else: numbers[nextNumberIndex] = abs(numbers[nextNumberIndex]) allSignCombinations(numbers, nextNumberIndex + 1) numbers[nextNumberIndex] = -numbers[nextNumberIndex] allSignCombinations(numbers, nextNumberIndex + 1) </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POAlgorithm to show all combinations of numbers in the list
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USrob mayoff
    1. USrob mayoff
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POAlgorithm to show all combinations of numbers in the list
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CO+1 for talking about the "algorithm" part of the question (instead of some example possible implementation...)
      singulars
      1. PO
      1. USheltonbiker
    2. COThanks! The explanation is great, it actually makes much more sense now, and the code is working exactly as I need it to (I did it in C#).
      singulars
      1. PO
      1. USAkira Iris
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload