Christian C15 - Scissors#44
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CheezItMan
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Jan 26, 2022
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A little awkward, but I think it mostly works. I made a few comments and let me know what questions you have.
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| def heap_sort(list): | ||
| """ This method uses a heap to sort an array. | ||
| Time Complexity: ? | ||
| Space Complexity: ? | ||
| Time Complexity: O(nlogn) (Each add is log(n), n nodes must be added) | ||
| Space Complexity: O(n) | ||
| """ |
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| print(self.store) |
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| def add(self, key, value=None): | ||
| """ This method adds a HeapNode instance to the heap | ||
| If value == None the new node's value should be set to key | ||
| Time Complexity: ? | ||
| Space Complexity: ? | ||
| Time Complexity: O(log(n)) : add tail is constant rebalancing is log(n) | ||
| Space Complexity: O(N+1) | ||
| """ |
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👍 However space complexity should be O(log n) due to the recursive call stack.
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| if index == 1 or index == 2: | ||
| parent_index = 0 | ||
| else: | ||
| parent_index = int(math.ceil((index-2)/2)) |
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I don't think you need the if statement, just the arithmetic for the parent_index would work.
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| print("Parent") | ||
| print(parent_index) | ||
| print(type(parent_index)) | ||
| print("index") | ||
| print(index) | ||
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Suggested change
| print("Parent") | |
| print(parent_index) | |
| print(type(parent_index)) | |
| print("index") | |
| print(index) |
| left_index = (index*2)+1 | ||
| right_index = (index*2)+2 | ||
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| if left_index >= len(self.store) or right_index >= len(self.store): |
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You can have a left child with no right child.
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| if left_index >= len(self.store) or right_index >= len(self.store): | |
| if left_index >= len(self.store) and right_index >= len(self.store): |
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| if self.store[left_index][0] < self.store[index][0]: | ||
| self.swap(left_index, index) | ||
| self.heap_down(index) | ||
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| elif self.store[right_index][0] < self.store[index][0]: | ||
| self.swap(right_index, index) | ||
| self.heap_down(index) |
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You shouldn't need to do two swaps here. I think you should compare the left and right children and swap the current index with the min child.
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Heaps Practice
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Comprehension Questions
heap_up&heap_downmethods useful? Why?