27.remove_elements.py

# 27. Remove Element
# Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. 
# The order of the elements may be changed. 
# Then return the number of elements in nums which are not equal to val.

# Consider the number of elements in nums which are not equal to val be k, to get accepted, 
# you need to do the following things:

# Change the array nums such that the first k elements of nums contain the elements which are not equal to val. 
# The remaining elements of nums are not important as well as the size of nums.
# Return k.

# Example 1:
# Input: nums = [3,2,2,3], val = 3
# Output: 2, nums = [2,2,_,_]
# Explanation: Your function should return k = 2, with the first two elements of nums being 2.
# It does not matter what you leave beyond the returned k (hence they are underscores).

# using pop method
def removeElement(nums, val):
    while val in nums:
        i=nums.index(val)
        nums.pop(i)
    return len(nums)

# using remove method
def removeElement(nums, val):
    while val in nums:
        nums.remove(val) # remove first occurence only
    return len(nums)

# using list comprehension
def removeElement(nums, val):
    nums[:] = [num for num in nums if num != val]