|
| 1 | +#!/usr/bin/env python |
| 2 | +importunittest |
| 3 | +importrandom |
| 4 | + |
| 5 | +# Import the compiled selectlib module. |
| 6 | +importselectlib |
| 7 | + |
| 8 | +classTestQuickselect(unittest.TestCase): |
| 9 | + |
| 10 | +defsorted_index_check(self,values,k): |
| 11 | +""" |
| 12 | + Helper function: Given a list and a target index k, |
| 13 | + use quickselect to partition the list in place, then verify |
| 14 | + that the element at index k equals the kth smallest element. |
| 15 | + """ |
| 16 | +# Create a copy of the original list to compute the sorted target. |
| 17 | +expected=sorted(values) |
| 18 | +# Call quickselect: this mutates the list in-place. |
| 19 | +selectlib.quickselect(values,k) |
| 20 | +# Check that the element at index k is what we expect. |
| 21 | +self.assertEqual(values[k],expected[k]) |
| 22 | + |
| 23 | +# Additionally, verify that all elements before index k are less than or equal |
| 24 | +# to the kth element, and all elements after index k are greater than or equal. |
| 25 | +kth_value=values[k] |
| 26 | +foriteminvalues[:k]: |
| 27 | +self.assertLessEqual(item,kth_value) |
| 28 | +foriteminvalues[k+1:]: |
| 29 | +self.assertGreaterEqual(item,kth_value) |
| 30 | + |
| 31 | +deftest_ordered_list(self): |
| 32 | +# Test on a sorted list. |
| 33 | +values=list(range(10)) |
| 34 | +k=5 |
| 35 | +selectlib.quickselect(values,k) |
| 36 | +self.assertEqual(values[k],5) |
| 37 | +# Check partition condition. |
| 38 | +foriteminvalues[:k]: |
| 39 | +self.assertLessEqual(item,values[k]) |
| 40 | +foriteminvalues[k+1:]: |
| 41 | +self.assertGreaterEqual(item,values[k]) |
| 42 | + |
| 43 | +deftest_reversed_list(self): |
| 44 | +# Test on a reverse-sorted list. |
| 45 | +values=list(range(10,0,-1)) |
| 46 | +k=3 |
| 47 | +self.sorted_index_check(values,k) |
| 48 | + |
| 49 | +deftest_random_list(self): |
| 50 | +# Test on a list of random integers. |
| 51 | +values= [random.randint(0,100)for_inrange(20)] |
| 52 | +k=random.randint(0,len(values)-1) |
| 53 | +self.sorted_index_check(values,k) |
| 54 | + |
| 55 | +deftest_with_duplicates(self): |
| 56 | +# Test on a list with duplicate values. |
| 57 | +values= [5,1,3,5,2,5,4,1,3] |
| 58 | +k=4 |
| 59 | +self.sorted_index_check(values,k) |
| 60 | + |
| 61 | +deftest_with_key_function(self): |
| 62 | +# Test the 'key' argument. |
| 63 | +# In this example, we use a simple key that returns the negative of the value, |
| 64 | +# effectively partitioning to find the kth largest element. |
| 65 | +values= [random.randint(0,100)for_inrange(15)] |
| 66 | +k=7# kth largest element if we sort descending |
| 67 | +# Make a copy for expected result. |
| 68 | +expected=sorted(values,key=lambdax:-x) |
| 69 | +# When using a key, quickselect should partition based on the key. |
| 70 | +selectlib.quickselect(values,k,key=lambdax:-x) |
| 71 | +self.assertEqual(values[k],expected[k]) |
| 72 | +kth_value=values[k] |
| 73 | +# Check that all prior items have keys less than or equal to the kth item. |
| 74 | +foriteminvalues[:k]: |
| 75 | +self.assertLessEqual(-item,-kth_value) |
| 76 | +foriteminvalues[k+1:]: |
| 77 | +self.assertGreaterEqual(-item,-kth_value) |
| 78 | + |
| 79 | +deftest_non_list_input(self): |
| 80 | +# Test that providing a non-list as values raises a TypeError. |
| 81 | +withself.assertRaises(TypeError): |
| 82 | +selectlib.quickselect("not a list",0) |
| 83 | + |
| 84 | +deftest_out_of_range_index(self): |
| 85 | +# Test that an out-of-range index raises an IndexError. |
| 86 | +values= [3,1,2] |
| 87 | +withself.assertRaises(IndexError): |
| 88 | +selectlib.quickselect(values,5) |
| 89 | + |
| 90 | +if__name__=='__main__': |
| 91 | +unittest.main() |