tech-interview-handbook/algorithms/array.md

Arrays

• In an arrays of arrays, e.g. given [[], [1, 2, 3], [4, 5], [], [], [6, 7], [8], [9, 10], [], []], print: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
  • Implement an iterator that supports hasNext(), next() and remove() methods.
• Given a list of item prices, find all possible combinations of items that sum a particular value K.
• Paginate an array with constraints, such as skipping certain items.
• Implement a circular buffer using an array.
• Given array of arrays, sort them in ascending order.
• Given an array of integers, print out a histogram of using said array; include a base layer (all stars)
  • E.g. [5, 4, 0, 3, 4, 1]

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• Given an array and an index, find the product of the elements of the array except the element at that index.
• Given a set of rectangles represented by a height and an interval along the y-axis, determine the size of its union.
• Given 2 separate arrays, write a method to find the values that exist in both arrays and return them.
• Given an array of integers find whether there is a sub-sequence that sums to 0 and return it.
  • E.g. [1, 2, -3, 1] => [1, 2, -3] or [2, -3, 1].
• Given an input array and another array that describes a new index for each element, mutate the input array so that each element ends up in their new index. Discuss the runtime of the algorithm and how you can be sure there would not be any infinite loops.
• Given an array of non-negative numbers, find continuous subarray with sum to S.
  • Source.
• Given an array of numbers list out all triplets that sum to 0. Do so with a running time of less than O(n^3).
  • Source.
• Given an array of numbers list out all quadruplets that sum to 0. Do so with a running time of less than O(n^4).
• Given an array of integers, move all the zeroes to the end while preserving the order of the other elements. You have to do it in-place and are not allowed to use any extra storage.
• Given an array of integers, find the subarray with the largest sum. Can you do it in linear time.
  • Maximum subarray sum problem.
• You have an array with the heights of an island (at point 1, point 2 etc) and you want to know how much water would remain on this island (without flowing away).
  • Trapping rain water question.
• Given an array containing only digits 0-9, add one to the number and return the array.
  • E.g. Given [1, 4, 2, 1] which represents 1421, return [1, 4, 2, 2] which represents 1422.
• Find the second maximum value in an array.
• Given an array, find the longest arithmetic progression.
• Rotate an array by an offset of k.
• Remove duplicates in an unsorted array where the duplicates are at a distance of k or less from each other.
• Given an unsorted list of integers, return true if the list contains any duplicates within k indices of each element. Do it faster than O(n^2).
• Given an unsorted list of integers, return true if the list contains any fuzzy duplicates within k indices of each element. A fuzzy duplicate is another integer within d of the original integer. Do it faster than O(n^2).
  • E.g. If d = 4, then 6 is a fuzzy duplicate of 3 but 8 is not.
• Say you have an unordered list of numbers ranging from 1 to n, and one of the numbers is removed, how do you find that number? What if two numbers are removed?
• Given an array of string, find the duplicated elements.
  • Source.
• Given an array of integers, find a maximum sum of non-adjacent elements.
  • E.g. [1, 0, 3, 9, 2] should return 10 (1 + 9).
  • Source
• Given an array of integers, modify the array by moving all the zeros to the end (right side). The order of other elements doesn't matter.
  • E.g. [1, 2, 0, 3, 0, 1, 2], the program can output [1, 2, 3, 1, 2, 0, 0].
  • Source.
• Given an array, return the length of the longest increasing contiguous subarray.
  • E.g., [1, 3, 2, 3, 4, 8, 7, 9], should return 4 because the longest increasing array is [2, 3, 4, 8].
  • Source.