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Ilya Kantor 2019-07-31 17:48:00 +03:00
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1-js/06-advanced-functions/01-recursion/article.md
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@ -326,18 +326,18 @@ In other words, a company has departments.
Now let's say we want a function to get the sum of all salaries. How can we do that?
An iterative approach is not easy, because the structure is not simple. The first idea may be to make a `for` loop over `company` with nested subloop over 1st level departments. But then we need more nested subloops to iterate over the staff in 2nd level departments like `sites`. ...And then another subloop inside those for 3rd level departments that might appear in the future? Should we stop on level 3 or make 4 levels of loops? If we put 3-4 nested subloops in the code to traverse a single object, it becomes rather ugly.
An iterative approach is not easy, because the structure is not simple. The first idea may be to make a `for` loop over `company` with nested subloop over 1st level departments. But then we need more nested subloops to iterate over the staff in 2nd level departments like `sites`... And then another subloop inside those for 3rd level departments that might appear in the future? If we put 3-4 nested subloops in the code to traverse a single object, it becomes rather ugly.
Let's try recursion.
As we can see, when our function gets a department to sum, there are two possible cases:
1. Either it's a "simple" department with an *array of people* -- then we can sum the salaries in a simple loop.
2. Or it's *an object with `N` subdepartments* -- then we can make `N` recursive calls to get the sum for each of the subdeps and combine the results.
1. Either it's a "simple" department with an *array* of people -- then we can sum the salaries in a simple loop.
2. Or it's *an object* with `N` subdepartments -- then we can make `N` recursive calls to get the sum for each of the subdeps and combine the results.
The (1) is the base of recursion, the trivial case.
The 1st case is the base of recursion, the trivial case, when we get an array.
The (2) is the recursive step. A complex task is split into subtasks for smaller departments. They may in turn split again, but sooner or later the split will finish at (1).
The 2nd case when we gen an object is the recursive step. A complex task is split into subtasks for smaller departments. They may in turn split again, but sooner or later the split will finish at (1).
The algorithm is probably even easier to read from the code: