|
| 1 | +""" |
| 2 | +Given an array of integers and an integer k, find the kth largest element in the array. |
| 3 | +
|
| 4 | +https://stackoverflow.com/questions/251781 |
| 5 | +""" |
| 6 | + |
| 7 | + |
| 8 | +def partition(arr: list[int], low: int, high: int) -> int: |
| 9 | + """ |
| 10 | + Partitions list based on the pivot element. |
| 11 | +
|
| 12 | + This function rearranges the elements in the input list 'elements' such that |
| 13 | + all elements greater than or equal to the chosen pivot are on the right side |
| 14 | + of the pivot, and all elements smaller than the pivot are on the left side. |
| 15 | +
|
| 16 | + Args: |
| 17 | + arr: The list to be partitioned |
| 18 | + low: The lower index of the list |
| 19 | + high: The higher index of the list |
| 20 | +
|
| 21 | + Returns: |
| 22 | + int: The index of pivot element after partitioning |
| 23 | +
|
| 24 | + Examples: |
| 25 | + >>> partition([3, 1, 4, 5, 9, 2, 6, 5, 3, 5], 0, 9) |
| 26 | + 4 |
| 27 | + >>> partition([7, 1, 4, 5, 9, 2, 6, 5, 8], 0, 8) |
| 28 | + 1 |
| 29 | + >>> partition(['apple', 'cherry', 'date', 'banana'], 0, 3) |
| 30 | + 2 |
| 31 | + >>> partition([3.1, 1.2, 5.6, 4.7], 0, 3) |
| 32 | + 1 |
| 33 | + """ |
| 34 | + pivot = arr[high] |
| 35 | + i = low - 1 |
| 36 | + for j in range(low, high): |
| 37 | + if arr[j] >= pivot: |
| 38 | + i += 1 |
| 39 | + arr[i], arr[j] = arr[j], arr[i] |
| 40 | + arr[i + 1], arr[high] = arr[high], arr[i + 1] |
| 41 | + return i + 1 |
| 42 | + |
| 43 | + |
| 44 | +def kth_largest_element(arr: list[int], position: int) -> int: |
| 45 | + """ |
| 46 | + Finds the kth largest element in a list. |
| 47 | + Should deliver similar results to: |
| 48 | + ```python |
| 49 | + def kth_largest_element(arr, position): |
| 50 | + return sorted(arr)[-position] |
| 51 | + ``` |
| 52 | +
|
| 53 | + Args: |
| 54 | + nums: The list of numbers. |
| 55 | + k: The position of the desired kth largest element. |
| 56 | +
|
| 57 | + Returns: |
| 58 | + int: The kth largest element. |
| 59 | +
|
| 60 | + Examples: |
| 61 | + >>> kth_largest_element([3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5], 3) |
| 62 | + 5 |
| 63 | + >>> kth_largest_element([2, 5, 6, 1, 9, 3, 8, 4, 7, 3, 5], 1) |
| 64 | + 9 |
| 65 | + >>> kth_largest_element([2, 5, 6, 1, 9, 3, 8, 4, 7, 3, 5], -2) |
| 66 | + Traceback (most recent call last): |
| 67 | + ... |
| 68 | + ValueError: Invalid value of 'position' |
| 69 | + >>> kth_largest_element([9, 1, 3, 6, 7, 9, 8, 4, 2, 4, 9], 110) |
| 70 | + Traceback (most recent call last): |
| 71 | + ... |
| 72 | + ValueError: Invalid value of 'position' |
| 73 | + >>> kth_largest_element([1, 2, 4, 3, 5, 9, 7, 6, 5, 9, 3], 0) |
| 74 | + Traceback (most recent call last): |
| 75 | + ... |
| 76 | + ValueError: Invalid value of 'position' |
| 77 | + >>> kth_largest_element(['apple', 'cherry', 'date', 'banana'], 2) |
| 78 | + 'cherry' |
| 79 | + >>> kth_largest_element([3.1, 1.2, 5.6, 4.7,7.9,5,0], 2) |
| 80 | + 5.6 |
| 81 | + >>> kth_largest_element([-2, -5, -4, -1], 1) |
| 82 | + -1 |
| 83 | + >>> kth_largest_element([], 1) |
| 84 | + -1 |
| 85 | + >>> kth_largest_element([3.1, 1.2, 5.6, 4.7, 7.9, 5, 0], 1.5) |
| 86 | + Traceback (most recent call last): |
| 87 | + ... |
| 88 | + ValueError: The position should be an integer |
| 89 | + >>> kth_largest_element((4, 6, 1, 2), 4) |
| 90 | + Traceback (most recent call last): |
| 91 | + ... |
| 92 | + TypeError: 'tuple' object does not support item assignment |
| 93 | + """ |
| 94 | + if not arr: |
| 95 | + return -1 |
| 96 | + if not isinstance(position, int): |
| 97 | + raise ValueError("The position should be an integer") |
| 98 | + if not 1 <= position <= len(arr): |
| 99 | + raise ValueError("Invalid value of 'position'") |
| 100 | + low, high = 0, len(arr) - 1 |
| 101 | + while low <= high: |
| 102 | + if low > len(arr) - 1 or high < 0: |
| 103 | + return -1 |
| 104 | + pivot_index = partition(arr, low, high) |
| 105 | + if pivot_index == position - 1: |
| 106 | + return arr[pivot_index] |
| 107 | + elif pivot_index > position - 1: |
| 108 | + high = pivot_index - 1 |
| 109 | + else: |
| 110 | + low = pivot_index + 1 |
| 111 | + return -1 |
| 112 | + |
| 113 | + |
| 114 | +if __name__ == "__main__": |
| 115 | + import doctest |
| 116 | + |
| 117 | + doctest.testmod() |
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