Arrays u0026 Strings: Two-Pointer and Sliding Window Techniques Quiz

Test your understanding of fundamental array and string manipulation concepts using the two-pointer and sliding window methods. This quiz covers key ideas and simple scenarios to boost your skills.

1. Identifying a Two-Pointer Situation

   Which scenario is best suited for applying the two-pointer technique in arrays?

   1. Sorting an array with quicksort
   2. Creating a hash map from an array
   3. Getting the length of the array
   4. Finding all pairs in a sorted array that sum to a target
   5. Counting the number of negative elements

2. Sliding Window Basics

   When using the sliding window method, what is the primary purpose of moving the window forward in a string?

   1. To build a frequency map
   2. To reverse the string
   3. To delete duplicates
   4. To analyze consecutive substring segments efficiently
   5. To check every possible permutation

3. Two-Pointer String Example

   Given the string 'level', what would a two-pointer approach help determine most efficiently?

   1. Whether the string is a palindrome
   2. Finding the shortest substring
   3. Sorting the string characters
   4. Replacing all spaces
   5. Counting the number of vowels

4. Subarray Sums Using Sliding Window

   What is the sliding window method especially useful for when working with a fixed-length subarray sum in arrays?

   1. Merging two arrays
   2. Quickly finding the maximum sum of any contiguous subarray of size k
   3. Finding unique elements
   4. Counting occurrences of a specific value
   5. Identifying sorted subarrays

5. Finding Duplicates with Two Pointers

   If you have a sorted array, how could the two-pointer approach assist in checking for duplicates?

   1. By reversing the array
   2. By comparing neighboring elements as the pointers move along the array
   3. By swapping random elements
   4. By counting all elements once
   5. By summing the array elements

6. Sliding Window for Longest Substring

   What does the sliding window technique help you find in the string 'abcabcbb'?

   1. If the string is sorted
   2. Longest substring without repeating characters
   3. Number of palindromic substrings
   4. Frequency of 'a'
   5. Position of the last character

7. Initial Pointers in Two-Pointer Technique

   When using two pointers on an array, where should the pointers typically be placed to start searching for pairs that add up to a sum?

   1. On two consecutive indices
   2. Only at the start
   3. At the beginning and end of the array
   4. Both at the middle index
   5. On random indices

8. Best Algorithm for Minimum Window Substring

   Which approach efficiently finds the smallest substring containing all characters of another string in 'ADOBECODEBANC' for 'ABC'?

   1. Counting sort
   2. Depth-first search
   3. Binary search
   4. Divide and conquer
   5. Sliding window

9. Shrinking the Window

   In a sliding window approach, how do you reduce the size of the window when the current window is valid but you seek a smaller one?

   1. Move both pointers backward
   2. Increase the window size
   3. Move the right pointer backward only
   4. Move the left pointer forward
   5. Restart the window from index zero

10. Two-Pointer for Array Reversal

    What does a two-pointer method help you achieve in an array when swapping the first and last elements and moving toward the center?

    1. Reverse the array in place
    2. Remove all zeros
    3. Calculate average value
    4. Compress duplicate values
    5. Sort the array in ascending order

11. Sliding Window - Variable Window Size

    In a sliding window with variable size, what triggers the window to expand or contract when searching for the smallest substring with given properties?

    1. Equalizing all window elements
    2. Randomly choosing to shrink the window
    3. Reaching the end of the string by default
    4. Sum of window elements is zero
    5. Meeting or not meeting a specific condition within the window

12. Optimizing with Sliding Window

    Why is the sliding window method typically more efficient than brute force for problems involving contiguous subarrays?

    1. It checks all possible combinations exhaustively
    2. It splits the array into halves
    3. It sorts the data first
    4. It uses recursion for each window
    5. It avoids redundant calculations by reusing information from the previous window

13. Two-Pointer Merge of Sorted Arrays

    What is the most efficient way to merge two sorted arrays into one sorted array using two pointers?

    1. Copy one array fully before the other
    2. Randomly select elements to combine
    3. Sort both arrays again individually before merging
    4. Reverse both arrays first
    5. Compare elements from both arrays simultaneously and pick the smaller one

14. Detecting Palindromes with Two Pointers

    Using two pointers, how would you check if the word 'racecar' is a palindrome?

    1. Swap every pair of characters
    2. Compare characters at the left and right pointers and move them towards the center
    3. Insert a space between each character
    4. Count total number of vowels
    5. Sort the string and compare to reversed version

15. Finding Fixed-Length Subarrays

    What kind of subarrays does the fixed-size sliding window method typically process in an array of numbers?

    1. Only subarrays with increasing values
    2. Every subarray of length k, in order
    3. Randomly selected subarrays
    4. Subarrays composed only of odd numbers
    5. Subarrays of all possible lengths

16. Key Benefit of Two-Pointer Technique

    What is a key advantage of using the two-pointer technique on a sorted array over using nested loops?

    1. Increases space usage significantly
    2. Reduces time complexity from O(n^2) to O(n)
    3. Removes duplicates automatically
    4. Guarantees sorting in place
    5. Allows random access to elements