Score array

Put scores in an array and print them.

Apply merge sort

Now we add a function that sorts the score array with merge sort. The init_scores function comes from the previous lesson and is called here.

Recall that merge sort runs in O(n log n) and is stable. We will use the merge helper to combine the two sorted halves.

The expected sorted array is [78, 85, 88, 90, 92]; correctly sorted from smallest to largest.

merge helper

merge(left, right) combines two sorted arrays. This helper was introduced in earlier sections; we reuse it here.

With two pointers we append the smaller to the result. Leftovers are copied to the end. The result is one sorted array.

Without this helper merge sort cannot work; that is why we include it in the project.

Exercise Sort scores

Write merge_sort_scores(scores). Print [78, 85, 88, 90, 92] with print(merge_sort_scores(init_scores())).

Show example solution

def merge(left, right):
    result = []
    i = j = 0
    while i < len(left) and j < len(right):
        if left[i] <= right[j]:
            result.append(left[i]); i += 1
        else:
            result.append(right[j]); j += 1
    result.extend(left[i:]); result.extend(right[j:])
    return result
def init_scores():
    # Return score array
    return [85, 92, 78, 90, 88]
def merge_sort_scores(scores):
    # Sort scores
    if len(scores) <= 1:
        return scores
    mid = len(scores) // 2
    left = merge_sort_scores(scores[:mid])
    right = merge_sort_scores(scores[mid:])
    return merge(left, right)
print(merge_sort_scores(init_scores()))

Test yourself

What is the sorted array?
- [85, 92, 78, 90, 88]
- [92, 90, 88, 85, 78]
- [78, 85, 88, 90, 92]
- [78, 88, 85, 90, 92]
Show answer

[78, 85, 88, 90, 92] — [78, 85, 88, 90, 92]

Base case

if len(scores) ____1:

Show answer

if len(scores) <=1:

Score array: match the terms

init_scores

Data
merge_sort_scores

Sort
merge

Helper
Result

[78,85,88,90,92]

Next lesson: Apply merge sort

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies