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Subsets.py
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Subsets.py
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from collections import deque
# Subsets
'''
Given a set with distinct elements, find all of its distinct subsets.
'''
from itertools import permutations
from operator import length_hint
def find_subsets(nums):
subsets = []
# start by adding the empty subset
subsets.append([])
for currentNumber in nums:
# we will take all existing subsets and insert the current
# number in them to create new subsets
n = len(subsets)
for i in range(n):
# create a new subset from the existing subset and
# insert the current element to it
set1 = list(subsets[i])
set1.append(currentNumber)
subsets.append(set1)
return subsets
def main():
print("Here is the list of subsets: " + str(find_subsets([1, 3])))
print("Here is the list of subsets: " + str(find_subsets([1, 5, 3])))
main()
# Subsets With Duplicates
'''
Given a set of numbers that might contain duplicates,
find all of its distinct subsets.
'''
def find_subsets(nums):
# sort the numbers to handle duplicates
list.sort(nums)
subsets = []
subsets.append([])
startIndex, endIndex = 0, 0
for i in range(len(nums)):
startIndex = 0
# if current and the previous elements are same, create new subsets only from the subsets
# added in the previous step
if i > 0 and nums[i] == nums[i - 1]:
startIndex = endIndex + 1
endIndex = len(subsets) - 1
for j in range(startIndex, endIndex+1):
# create a new subset from the existing subset and add the current element to it
set1 = list(subsets[j])
set1.append(nums[i])
subsets.append(set1)
return subsets
def main():
print("Here is the list of subsets: " + str(find_subsets([1, 3, 3])))
print("Here is the list of subsets: " + str(find_subsets([1, 5, 3, 3])))
main()
# Permutations
'''
Given a set of distinct numbers, find all of its permutations.
Permutation is defined as the re-arranging of the elements of the set
'''
def find_permutations(nums):
result = []
# TODO: Write your code here
length_nums = len(nums)
permutations = deque()
permutations.append([])
for currentNumber in nums:
n = len(permutations)
for _ in range(n):
oldPermutation = permutations.popleft()
for j in range(len(oldPermutation)+1):
newPermutation = list(oldPermutation)
newPermutation.insert(j, currentNumber)
if len(newPermutation) == length_nums:
result.append(newPermutation)
else:
permutations.append(newPermutation)
return result
def main():
print("Here are all the permutations: " +
str(find_permutations([1, 3, 5])))
main()
# Permutations (recursively)
def find_permutations(nums):
result = []
generate_permutations_recursive(nums, 0, [], result)
return result
def generate_permutations_recursive(nums, index, currentPermutation, result):
if index == len(nums):
result.append(currentPermutation)
else:
for i in range(len(currentPermutation)+1):
newPermutation = list(currentPermutation)
newPermutation.insert(i, nums[index])
generate_permutations_recursive(
nums, index + 1, newPermutation, result)
def main():
print("Here are all the permutations: " +
str(find_permutations([1, 3, 5])))
main()
# String Permutations by changing case
'''
Given a string, find all of its permutations
preserving the character sequence but changing case.
'''
def find_letter_case_string_permutations(input):
permutations = [input]
for i in range(len(input)):
if input[i].isalpha():
n = len(permutations)
for j in range(n):
characters = list(permutations[j])
characters[i] = characters[i].swapcase()
permutations.append("".join(characters))
return permutations
def main():
print("String permutations are: " +
str(find_letter_case_string_permutations("ad52")))
print("String permutations are: " +
str(find_letter_case_string_permutations("ab7c")))
main()