Embercode: AI-powered software engineer course

1. What does this program print? ``

python
counts = {}
s = 'eceba'
left = 0
distinct = 0
best = 0
for right, c in enumerate(s):
    before = counts.get(c, 0)
    counts[c] = before + 1
    if before == 0:
        distinct += 1
    while distinct > 2:
        out = s[left]
        remaining = counts[out] - 1
        if remaining == 0:
            del counts[out]
            distinct -= 1
        else:
            counts[out] = remaining
        left += 1
    best = max(best, right - left + 1)
print(best, distinct)

``

3 23 32 23 1

2. What does this program print? ``

python
counts = {'a': 1}
print('sum with get: ' + str(counts.get('z', 0) + 1))
n = counts['z']
print(n)

``

It prints 1, then NoneIt prints sum with get: 1, then raises KeyError: 'z' on the counts['z'] lineIt prints sum with get: 0, then prints 0It raises IndexError before printing anything

3. Which dict method returns a default value for a missing key, so the code never gets an error?

Type your answer.

4. Write the formula for the length of a window that runs from index left to index right, with both ends included.

Type your answer.

5. In the eceba trace with k = 2, the window removes the e at index 0, but the key 'e' stays in the dict. Why?

Because e is the first letter, and a dict never removes its first keyBecause get adds the key back after every stepBecause the window still holds another e, so its count only drops from 2 to 1Because distinct is always the same as len(counts)

Frequency windows