Questions tagged [arrays]
A sequential random-access data structure whose size can typically not be changed after creation.
426
questions
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1answer
34 views
How to find the size of gaps between entries in an array so that the first and last element of the array is filled and the gaps are all of equal size?
I have an array a of n entries. I need to place a token on the first and last position of that array, so a[0] = 1 and a[n-1] = 1....
2
votes
1answer
60 views
Returning random integer from interval based on last result and a seed
Suppose we have an interval of integers [a, b]. I would like to have a function that returns random members from within the interval, without repetitions. Once that all members within the interval are ...
2
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1answer
30 views
How do you find all integers in a sorted array of size n that appear n/k times?
I try to find the solution to this problem:
How do you find all integers in a sorted array of size n that appear n/k times in less than O(klogn) time?
I could only find this question, where O(klogn) ...
2
votes
1answer
40 views
Smallest subarray problem
Say you have an array of integers like [1, 2, 3, 4, 5, 6], the problem is to find the smallest way to break up the array into sub-arrays where each sub-array satisfies the following requirement:
sub-...
1
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1answer
35 views
Find position in array where element-wise multiplication with string of 1 and 0s results in max value
I have a sequence of 1s and 0s. For example: $bits = [1, 0, 1, 1, 1, 0]$. I also have an array of positive integers. For example $arr = [12, 23, 4, 6, 8, 0, 24, 72]$. I need to find the index, $i$, in ...
0
votes
0answers
15 views
How to pick a random index in an array based on the index's value?
While solving a problem on leetcode, I used a heap to give the largest probable value. The problem statement is as follows:
Given an array w of positive integers, where w[i] describes the weight of ...
3
votes
0answers
45 views
Minimizing the sum of differences in a pair [duplicate]
You have two arrays, a and b
Both contain n elements, all positive and distinct.
you have to create a pair, by taking one number from each array, such that the sum of the differences of the pairs ...
1
vote
2answers
43 views
Amortized time for dynamic array
I'm struggling to understand one part from the book "Cracking the coding interview".
The author states inserting an element in a dynamic array is $O(1)$ most of the time, except when the array is full ...
0
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0answers
30 views
Choosing potential function in amortized analysis of the dynamic array
Suppose we have a dynamic array with some initial capacity $c_{initial}$ (i.e., the dynamic array with zero elements will have this capacity). The $add$ operation is modified the following way:
New ...
2
votes
2answers
49 views
Finding largest farthest increasing pairs in array?
Is there a simple linear algorithm for finding in an array A two such elements that $A[i] > A[j]$ and $i - j$ is as large as possible? If one wants to actually return the indices, then linear ...
2
votes
2answers
84 views
Managing an hotel using AVL trees - Data Structures
I have a Data Structure question where I need to manage an hotel, each room has a number between $1-n$
and it can be occupied or not.
Available Data structures: AVL* Trees, B-Trees, Arrays, Stacks, ...
2
votes
1answer
46 views
Algorithm for splitting an array into k sub-arrays
We want implement a data structure that have the following methods: Init(A,k)- Gets an array A with n different values and initialize our data structure that so it will divide A into k equally sized ...
0
votes
1answer
22 views
Maximum Circular Subarray sum
This is a question from the book Algorithms by Jeff Erickson.
Suppose A is a circular array. In this setting, a “contiguous subarray” can be either an interval A[i .. j] or a suffix followed by a ...
1
vote
1answer
31 views
How to mathematically determine row, column, and sub-square of cell in nxn array where n is a perfect square?
Given an one dimensional array of size nxn, where n is a perfect square
How can one mathematically determine the row, column, and/or sub-square the cell resides in? Additionally, is there a ...
1
vote
2answers
34 views
Given a list of integers and a target integer, return the number of triplets whose product is the target integer and two adjacent triplets
Question: Given a list of integers (possibly negative) and a target integer, return the number of triplets whose product is the target integer and two of the triplets must be adjacent.
More ...
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1answer
42 views
Efficient algorithm to compare arrays problem
I was submitted an interesting problem, but I wasn't able to find a solution.
Define a function p(x, y) that takes int x and y, with ...
1
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0answers
28 views
Matrix multiplication over range in $O(n)$
Let $Q$ denote the number of queries.
I have a $25 \times 25$ matrix in each cell of an array of size $n$. Let us denote this array by $A$. It's a special matrix, more specifically, all elements are $...
1
vote
1answer
30 views
Why does a range query on a segment tree return at most $\lceil \log_2{N} \rceil$ nodes?
If an array $A[1 \ldots N]$ is represented using a segment tree having sets in each interval, why does a range query $[L\ldots R]$ returns at most $\lceil \log_2{N} \rceil$ sets (or disjoint intervals)...
1
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2answers
37 views
Find combination of vectors from array that sum up to s
I have an array of $n$ $m$-dimensional vectors (in my case, they're 27 dimensional). I also have an $m$-dimensional vector $s$. I want to find all combinations of $k$ vectors from my array whose ...
1
vote
1answer
27 views
Longest subarray with at most two different values - Runtime complexity for a DP solution
Consider the problem of finding, for a given input array, the longest subarray with at most two different values.
For example:
...
4
votes
1answer
55 views
Find two contiguous subarrays with the greatest difference
Here's an interview question I've seen on a few sites. People claim that an O(n) solution is possible, but I've been racking my brain these last 2 days and I couldn'...
0
votes
3answers
83 views
Formal definition of the Dynamic Array - what is the Dynamic Array
I've researched quite a bit about this topic. Since I'm kind of a fan of Exact Sciences, I love everything to have a crystal-clear and determined definition, without any ambiguous or dubious points.
...
0
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0answers
24 views
Options for approaching stable marriage problem with unequally sized sets of elements/preferences
I am looking for an algorithm/code that will provide stable matching for two unequally sized sets of elements (clubs and students) with an unequal set of preferences. There is a large pool of students ...
1
vote
1answer
56 views
Generate all combinations of a set/array with specific conditions
Apologies if this isn't posted in the right stack exchange, but I'm trying to come up with an algorithm that generates a set of sets ('set' as synonymous with 'array') with the following conditions:
...
0
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2answers
66 views
Can you insert into sorted list with time O(1)?
Wondering if this was possible. If I have a sorted list, can I find the right spot for an integer and insert it, all in O(1) time? The only way I can think to do this is via having a MASSIVE hashmap ...
5
votes
1answer
271 views
Why is memory one dimensional?
Addresses in system programming languages like C are one dimensional (i.e. one number). This forces the programmer to make a decision whether matrices are stored "row major" or "column major" causing ...
1
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1answer
50 views
How to shift a matrix by x rows and y columns in the most efficient way?
My objective is to shift rows by x and columns by y in a 2d matrix. My problem is to solve this objective in an efficient manner.
x and y could be negative or positive. Negative would mean up/left ...
1
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0answers
13 views
Minimising total access time to elements in an array which is accessed sequentially
Starting with two examples:
for(i = 1; i<10; i++) {B[i] = 0;}
for(i = 1; i<10; i++) {B[2i] = 0;}
In the first example, ...
1
vote
1answer
45 views
Is it possible to find a supersequence of a single array?
In Jeff Erickson's Algorithms textbook, the chapter on Dynamic Programming asks you to "Describe an efficient algorithm to compute the length of the shortest
oscillating supersequence of an arbitrary ...
2
votes
1answer
38 views
Finding largest sum of $k$ elements below threshold
I was working on a project and am stuck in the middle unable to find an optimal method to solve this problem. Consider an array $A$ of $n$ elements. I have to choose $k$ elements such that the sum of ...
0
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0answers
30 views
Reverse of In-place algorithm for interleaving an array
How to do the reverse process of In-place algorithm for interleaving an array question?
1
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1answer
97 views
Array segmenting algorithm
I have a sorted array of integers [x, ..., n, ..., y] so that
x > 0
n - x = random positive integer
The array might look something like this:
[1, 2, 3, 15, 16, 17, 120, 121, 122, 123, 124, 125, 126,...
0
votes
1answer
45 views
$ \Omega(m)$ and $O(m)$ meaning in theorem proof about dynamic array complexity
My algorithms and data structures' book states that to create a dynamic array the following procedure is followed:
Let $d$ be the length of an array $ a $ and $n $ the number of elements stored in ...
2
votes
1answer
31 views
Minimum moves to “stabilize” an array
We have given an array of size $N$, consisting of positive integers, and an integer $H$. We also know that an array is stable iff $|A_i - A_{i-1}| \leq H$ for each $1<i<N-1$. We can modify the ...
1
vote
1answer
44 views
What algorithms for unification over (multidimensional) array terms?
I am looking for references on implementing unification over multidimensional array terms.
Are there specialized unification algorithms for those cases? I wasn't able to find satisfactory literature ...
0
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1answer
40 views
pseudocode to split number value to array of numbers
How to write a pseudocode to split a number value to array of numbers? Let's say the number value is 12345. I need to convert it into [1,2,3,4,5].
-1
votes
1answer
140 views
Time complexity of removing duplicates in lists
Question
I am wondering what is the minimum time complexity of get the unique value of a array in two conditions: keep the order or not.
For example, suppose we have a original array ...
5
votes
1answer
700 views
How can merging two sorted arrays of N items require at least 2N - 1 comparisons in every case?
The HW question, on page 362 of Data Structures and Algorithms in C++: Fourth Editionby Mark Allen Weiss, reads as follows:
Prove that merging two sorted arrays of N items requires at least 2 * N - ...
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1answer
712 views
Minimum number of cans needed to carry all used water
so I've just attempted an online technical test. It was on hacker rank however I'm sure leetcode usually has the same (and more) so thought i'd ask.
I could not think of a nice solution and cannot ...
1
vote
0answers
75 views
finding the parent index in an interval heap (stored on an array) given a child index
an interval heap is a binary tree stored on an array where the size of each node is 2.
i would like to be able to find the index of a parent and find one of the child indices given the index of a ...
1
vote
1answer
86 views
Find number of triples that sum up to zero in query-intervals
My problem is that we have an array of $N$ integers $(N <=5000)$ on the interval $[-10^6,10^6]$. We also have $Q$ queries $(Q <= 10^5)$ giving us some range in the array.
For each query, we ...
0
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0answers
77 views
Selection Sort vs Merge Sort
I recently wrote a written test for the recruitment of Scientists/Engineers in ISRO(Indian Space Research Organization) few days back and the following question appeared in the test.
Of the following ...
0
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0answers
25 views
Maximising sum of associated elements
I have a set of elements. Each element is connected with every other element by a path of length $l_i,_j\geq0$ (where i$\neq$j).
I have to calculate the maximum sum of path length such that I should ...
1
vote
2answers
285 views
Sorting a large list of test scores
You have a large list (say N > 10000) of test scores which you would like to sort. The test scores are between 1 and 100. What is quickest way to sort the list?
First thought. We have a O(N log N) ...
1
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0answers
16 views
When was the dynamic array first introduced as an example for amortized analysis?
I'm writing a report on amortized analysis, and I'm using the example of a dynamic array to explain each method. I think it would be nice to add a reference to when this example was first used, as it ...
0
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1answer
122 views
Which sort algorithm to choose given two specific arrays?
Interview question:
Given array A which contains only odd numbers and array B which contains only even numbers, explain
which sort algorithm would you choose.
I said merge sort. I thought that ...
1
vote
1answer
224 views
Selecting elements from two arrays to get a target sum
Let $A$ and $B$ be two arrays of size $n$ with positive integer values. Let $k$ be a given positive integer.
Design an algorithm to solve the following problem.
For each index $i$ ($1\leq i \leq n$)...
4
votes
1answer
101 views
Sort array of duplicate integers in place
Given an array of integers within [1, n] where n = size of array, some elements may appear more than once.
Could we sort it with just 1 extra space and in O(n) time?
2
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0answers
38 views
Find a non-minimal sequence of elements covering the support set
Consider a sequence $s$ of $n$ integers (let's ignore the specifics of their representation and just suppose we can read, write and compare them in $O(1)$ time with arbitrary positions). Denote $\text{...
0
votes
1answer
129 views
Given an array arr[] of N integers. Do the following operation n-1 times
For every Kth operation:
Right rotate the array clockwise by 1.
Delete the (n-k+1)th last element.
eg:
A = {1, 2, 3, 4, 5, 6}. Rotate the array clockwise i.e. after rotation the array A = {6, 1, 2, ...
