30-day-leetcoding-challenges

product_of_array_except_self.py

#   Product of Array Except Self
def productExceptSelf(nums):
    size = len(nums)
    result = [1] * size      
    left = 1
    right = 1
  
    for i in range(size):
        result[i] *= left
        result[-1-i] *= right
        left *= nums[i]
        right *= nums[-1-i]
  
    return result

if __name__ == '__main__':
    print(productExceptSelf([1, 2, 3, 4]))

single_number.py

# Given a non-empty array of integers, every element appears twice except for one. 
# Find that single one.
# Example: input [1, 2, 3, 2, 3] => output 1

# Explain:
# a ^ 0 => a
# a ^ a => 0
# [a, b, a] => a ^ b ^ a = (a ^ a) ^ b => b
def single_number(nums):
    return reduce(lambda x, y: x^y, nums)