Circular Counter
a = ['1', '2', '3', '4', '5', '6', '7', '8', '9']
def circ_counter(int_list, skip):
skip = skip - 1 # list starts with 0 index
idx = 0
while len(int_list) > 0:
# hashing to keep changing the index to every 3rd
idx = (skip + idx) % len(int_list)
print(int_list.pop(idx))
circ_counter(a, 3)
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Flatten Array
from functools import reduce
def list_flatten(l):
def flatten(pv, cv):
if not isinstance(cv, list):
return pv + [cv]
else:
return pv + list_flatten(cv)
return reduce(flatten, l, [])
print(list_flatten([2, 1, [3, [4, 5], 6], 7, [8]]))
print('output should be [2, 1, 3, 4, 5, 6, 7, 8]')
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Three Sum Array
# TODO: FFT implementation for MlogM algo
def three_sum(nums):
res = []
nums.sort()
for i in range(len(nums) - 2):
if i > 0 and nums[i] == nums[i - 1]:
continue
l, r = i + 1, len(nums) - 1
while l < r:
s = nums[i] + nums[l] + nums[r]
if s > 0:
r -= 1
elif s < 0:
l += 1
else:
# found three sum
res.append([nums[i], nums[l], nums[r]])
# remove duplicates
while l < r and nums[l] == nums[l + 1]:
l += 1
while l < r and nums[r] == nums[r - 1]:
r -= 1
l += 1
r -= 1
return res
if __name__ == "__main__":
x = [-1, 0, 1, 2, -1, -4]
print("input: ", x)
print("output should be: ", [[-1, -1, 2], [-1, 0, 1]])
print("output: ", three_sum(x))
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Summary Ranges
def summary_ranges(nums):
res = []
l = len(nums)
if l == 1:
return [str(nums[0])]
i = 0
while i < l:
start = nums[i]
while i + 1 < l and nums[i + 1] - nums[i] == 1:
i += 1
if nums[i] != start:
res.append(str(start) + "->" + str(nums[i]))
else:
res.append(str(start))
i += 1
return res
a = [0, 1, 2, 4, 5, 7]
print("input: ")
print(a)
print("output should be")
print(["0->2", "4->5", "7"])
print("output: ")
print(summary_ranges(a))
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Rotate Arrays
def rotate(arr, k):
n = len(arr)
k = k % n
return arr[n - k:] + arr[:n - k]
a = [1, 2, 3, 4, 5, 6, 7]
print("in: ", a)
print("expected: ", [5, 6, 7, 1, 2, 3, 4])
print("out: ", rotate(a, 3))
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Longest Non Repeat
from typing import Dict
def longest_non_repeat(s: str) -> int:
start, maxlen = 0, 0
used_char = {} # type: Dict[str, int]
for i, char in enumerate(s):
if char in used_char and start <= used_char[char]:
start = used_char[char] + 1
else:
maxlen = max(maxlen, i - start + 1)
used_char[char] = i
return maxlen
a = "abcabcdefbb"
print("input: ", a)
print("result: ", longest_non_repeat(a))
print("output should be 6")
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Missing Ranges
def missing_ranges(arr, low, high):
hashed = set(arr)
for n in range(low, high):
if n not in hashed:
print(n)
inpt = [10, 12, 11, 15]
low, hi = 10, 15
print("input: ", inpt)
print("result: ")
missing_ranges(inpt, low, hi)
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