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How to practice algorithms with tryalgo

• miscellaneous •

Hey, if you want to improve your skills in algorithmic problem solving, you don’t even need an online judge!

In the tryalgo repository, we have provided tests for 128 classic algorithms.

Howto

First, clone the tryalgo repo.

$ git clone https://github.com/jilljenn/tryalgo
$ cd tryalgo

Then check that the tests pass:

$ python3 -m unittest
...........................................................................................
----------------------------------------------------------------------
Ran 91 tests in 2.570s

OK

If you want to practice union of rectangles for example, open tryalgo/union_rectangles.py and DELETE1 the content of the algorithm.

def union_rectangles(R):
    """Area of union of rectangles

    :param R: list of rectangles defined by (x1, y1, x2, y2)
       where (x1, y1) is top left corner and (x2, y2) bottom right corner
    :returns: area
    :complexity: :math:`O(n^2)`
    """
    # OMG I am so deleted, doushiyou

The tests should fail now.

$ python3 -m unittest
.........................................................................................F.
======================================================================
FAIL: test_union_rectangles (tests.test_tryalgo.TestTryalgo)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/jilljenn/code/tryalgo/tests/test_tryalgo.py", line 1582, in test_union_rectangles
    self.assertEqual(union_rectangles([]), 0)
AssertionError: None != 0

----------------------------------------------------------------------
Ran 91 tests in 2.939s

FAILED (failures=1)

Rewrite that algorithm the best you can, until the tests pass.

Enjoy!

You can also write your own tests in tests/test_tryalgo.py, and potentially create a PR if you find a corner case that we did not think about!

  1. Don’t be afraid to break everything, this is a git repository so everything is versioned; if you want to recover the initial file (and know the solution), you can do:

    $ git checkout tryalgo/union_rectangles.py

    ↩

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