mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-12-18 17:20:16 +00:00
f17e9822b0
* psf/black changes to next_greater_element.py
* fixup! Format Python code with psf/black push
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
99 lines
2.8 KiB
Python
99 lines
2.8 KiB
Python
arr = [-10, -5, 0, 5, 5.1, 11, 13, 21, 3, 4, -21, -10, -5, -1, 0]
|
|
expect = [-5, 0, 5, 5.1, 11, 13, 21, -1, 4, -1, -10, -5, -1, 0, -1]
|
|
|
|
|
|
def next_greatest_element_slow(arr: list) -> list:
|
|
"""
|
|
Get the Next Greatest Element (NGE) for all elements in a list.
|
|
Maximum element present after the current one which is also greater than the
|
|
current one.
|
|
>>> next_greatest_element_slow(arr) == expect
|
|
True
|
|
"""
|
|
result = []
|
|
for i in range(0, len(arr), 1):
|
|
next = -1
|
|
for j in range(i + 1, len(arr), 1):
|
|
if arr[i] < arr[j]:
|
|
next = arr[j]
|
|
break
|
|
result.append(next)
|
|
return result
|
|
|
|
|
|
def next_greatest_element_fast(arr: list) -> list:
|
|
"""
|
|
Like next_greatest_element_slow() but changes the loops to use
|
|
enumerate() instead of range(len()) for the outer loop and
|
|
for in a slice of arr for the inner loop.
|
|
>>> next_greatest_element_fast(arr) == expect
|
|
True
|
|
"""
|
|
result = []
|
|
for i, outer in enumerate(arr):
|
|
next = -1
|
|
for inner in arr[i + 1 :]:
|
|
if outer < inner:
|
|
next = inner
|
|
break
|
|
result.append(next)
|
|
return result
|
|
|
|
|
|
def next_greatest_element(arr: list) -> list:
|
|
"""
|
|
Get the Next Greatest Element (NGE) for all elements in a list.
|
|
Maximum element present after the current one which is also greater than the
|
|
current one.
|
|
|
|
A naive way to solve this is to take two loops and check for the next bigger
|
|
number but that will make the time complexity as O(n^2). The better way to solve
|
|
this would be to use a stack to keep track of maximum number giving a linear time
|
|
solution.
|
|
>>> next_greatest_element(arr) == expect
|
|
True
|
|
"""
|
|
stack = []
|
|
result = [-1] * len(arr)
|
|
|
|
for index in reversed(range(len(arr))):
|
|
if len(stack):
|
|
while stack[-1] <= arr[index]:
|
|
stack.pop()
|
|
if len(stack) == 0:
|
|
break
|
|
|
|
if len(stack) != 0:
|
|
result[index] = stack[-1]
|
|
|
|
stack.append(arr[index])
|
|
|
|
return result
|
|
|
|
|
|
if __name__ == "__main__":
|
|
from doctest import testmod
|
|
from timeit import timeit
|
|
|
|
testmod()
|
|
print(next_greatest_element_slow(arr))
|
|
print(next_greatest_element_fast(arr))
|
|
print(next_greatest_element(arr))
|
|
|
|
setup = (
|
|
"from __main__ import arr, next_greatest_element_slow, "
|
|
"next_greatest_element_fast, next_greatest_element"
|
|
)
|
|
print(
|
|
"next_greatest_element_slow():",
|
|
timeit("next_greatest_element_slow(arr)", setup=setup),
|
|
)
|
|
print(
|
|
"next_greatest_element_fast():",
|
|
timeit("next_greatest_element_fast(arr)", setup=setup),
|
|
)
|
|
print(
|
|
" next_greatest_element():",
|
|
timeit("next_greatest_element(arr)", setup=setup),
|
|
)
|