Two Pointers Quiz

8 questions10 minPass: 60%+10 XP on first pass

Opposite-end pointers, in-place read/write pointers, 3Sum and Container With Most Water.

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Question 1
What must usually be true of an array to use opposite-end two pointers for a pair sum?
It is sortedIt has no duplicatesIt has an even lengthAll values are positive
Question 2
In Two Sum II (sorted array), the current sum is SMALLER than the target. What do you do?
Move the left pointer rightMove the right pointer leftMove both pointersRestart from the beginning
Question 3
What is the time and extra space of two-pointer Two Sum on a sorted array?
O(n²) time, O(1) spaceO(n) time, O(1) spaceO(n) time, O(n) spaceO(log n) time, O(1) space
Question 4
In Container With Most Water, which pointer should move?
Always the left oneThe taller lineThe shorter lineBoth, alternately

Question 5

What does nums look like after this code runs on [0, 1, 0, 3, 12]?

write = 0
for read in range(len(nums)):
    if nums[read] != 0:
        nums[write], nums[read] = nums[read], nums[write]
        write += 1

[0, 0, 1, 3, 12][1, 3, 12, 0, 0][12, 3, 1, 0, 0][1, 0, 3, 0, 12]

Question 6Select all that apply
Why does 3Sum sort the array first? (select all that apply)
To use two pointers for the remaining pairTo skip duplicate values easilyBecause the output must be sortedTo make it O(n)
Question 7
When merging two sorted arrays into the first array's extra space, from which end do you fill?
From the startFrom the endFrom the middleIt doesn't matter
Question 8
Is "racecar" a palindrome? Type yes or no.