Two Pointers — Reasoning Check

1. Sorted two-sum has active values [-4,-1,2,5,9] and target 8. The endpoint sum is 5. Why can the left endpoint -4 be discarded?

Select one answer.

The right endpoint 9 is above the target and must be discarded first. Any negative value can be removed when the target is positive. Every remaining partner for -4 is at most 9, so every such sum is below 8.

2. What is the maximum container area for heights [4,1,3,2]? Enter one integer.

3. Sort Colors uses the four regions zeros | ones | unknown | twos. It begins with [2,1,1,0], low=0, mid=0, high=3. After its branch for nums[mid]==2, which state preserves those regions?

Select one answer.

Array [0,1,1,2], low=0, mid=1, high=2. Array [0,1,1,2], low=1, mid=0, high=2. Array [0,1,1,2], low=0, mid=0, high=2.

4. How many unique zero-sum value triples does [-2,0,0,2,2] contain? Enter one integer.

5. To decide whether s="aba" is a subsequence of t="abxba", a scan has matched "ab" when it reads x. Which state should survive this mismatch?

Select one answer.

Advance both pointers because a text mismatch consumes one requested byte. Keep the two matched bytes and advance only the text pointer. Reset the matched-prefix length to zero and advance the text pointer.

6. A valid ASCII-palindrome routine ignores non-alphanumeric bytes but keeps digits. Does "2aA2!" pass? Enter true or false.