Embercode: AI-powered software engineer course

1. The sort_colours function below groups a list of 0s, 1s and 2s in one pass. What does this print? ``

python
def sort_colours(nums):
    low = mid = 0
    high = len(nums) - 1
    while mid <= high:
        if nums[mid] == 0:
            nums[low], nums[mid] = nums[mid], nums[low]
            low += 1
            mid += 1
        elif nums[mid] == 1:
            mid += 1
        else:
            nums[mid], nums[high] = nums[high], nums[mid]
            high -= 1

nums = [2, 1, 0, 2, 0]
sort_colours(nums)
print(nums)

``

[0, 0, 1, 2, 2][0, 1, 0, 2, 2][2, 1, 0, 2, 0][0, 0, 2, 2, 1]

2. The product_except_self function below returns, for each index, the product of all the other values. What does this print? ``

python
def product_except_self(nums):
    n = len(nums)
    result = [0] * n
    prefix = 1
    for i in range(n):
        result[i] = prefix
        prefix *= nums[i]
    suffix = 1
    for i in range(n - 1, -1, -1):
        result[i] *= suffix
        suffix *= nums[i]
    return result

print(product_except_self([3, 0, 2, 5]))

``

[0, 0, 0, 0][30, 30, 30, 30][0, 15, 0, 0][0, 30, 0, 0]

3. This version of product_except_self has one change in its second loop. What does print(wrong_equals([2, 3, 4])) print? ``

python
def wrong_equals(nums):
    n = len(nums)
    result = [0] * n
    prefix = 1
    for i in range(n):
        result[i] = prefix
        prefix *= nums[i]
    suffix = 1
    for i in range(n - 1, -1, -1):
        result[i] = suffix
        suffix *= nums[i]
    return result

``

[12, 8, 6][12, 4, 1][24, 8, 6][1, 4, 12]

4. Put the steps of product_except_self in the order the function runs them.

Use the arrows to put the steps in order.

1.Walk from left to right, storing the running product in result[i] and then multiplying it by nums[i]
2.Walk from right to left, multiplying result[i] by the running suffix and then multiplying the suffix by nums[i]
3.Return result, a new list, so nums has not changed
4.Create result as a new list of zeros with the same length as nums, and start the running product at 1

5. Put the steps of the check against sorted() from the partition lesson in the order they run.

Use the arrows to put the steps in order.

1.Make a sorted copy of the list with sorted()
2.Compare the two with == and count any mismatch
3.Run sort_colours on the original list
4.Make a random list with random.Random(42) and a length from 0 to 12

Partition and product