Questions tagged [stacks]

A stack is a Last In First Out (LIFO) data structure. A common use of stacks is to store subroutine arguments and return addresses.

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Implement Immediate Smaller Element problem using Stack

Immediate Smaller Element Problem: Given an integer array arr of size $n$. For each element in the array, check whether the right adjacent element (on the next ...
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Why divide a stack into two parts and store them separately in main-memory and hard-drive a bad idea?

I'm learning data structure and trying to solve problem related to Computer Game like Chess/Go. There is a line in my book on the section of DFS algorithm, which is implemented by two stacks: one for ...
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write adt for stack operations

Ok, I dont understand whats the difference between: write code for stack operations and write adt for stack operations? lets say the operation is push() and pop(). So what different code is to be ...
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Black-Box Machine

Suppose we have mysterious machine which return median $m$ of given set $S$ and set $S/\{m\}$ in constant time, where $S/\{m\}$ denotes the difference of $S$ and element $m$. Prove that we can sort ...
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How to draw the heap for an array in Java?

I have an assignment to draw the heap after an ArrayList and a LinkedList is created. ...
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How to convert a recursive function to a non recursive one using stack while keeping memoization?

Let's say I want to count the number of ways a string can be decoded, once encoding algorithm follows this map: 'a'=>'1', 'b'=>'2', ... 'z'=>'26'. I could ...
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How does the OS handle multiple stacks in its physical memory?

Without assuming ASLR... Processes have virtual addresses, and they manage stacks & heaps of their own. However, these all get mapped to physical addresses somewhere on the memory. Let's say we ...
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Automatic stack

Each context-free language has an automatic stack received by a non-deterministic blank. That is, it will not uphold the following determinism requirement:
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Call stack is hard to maintain in my brain. What should I?

When I study Binary Search Tree, I try to use a pencil and paper to scratch the process of in-order traversal. However, I find that it is hard to maintain the call stack in my brain without paper and ...
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Is there a known way to make an efficient, compact, and fully persistent stack or queue?

In the world of mutable/ephemeral data structures and imperative programming languages, one of the classic ways to implement a stack or queue is to use array doubling: use mutation to fill up or empty ...
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Same computation order using postfix notation?

I'm trying to understand arithmetic using stacks. Specifically converting infix notation to postfix notation. My question is how you convert an expression like: 1 + (2 + 3) + (4 + 5) that computes in ...
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Formal definition of a language accepted by PDA

I am a bit confused on how to give a formal definition of the language accepted by A? I can describe it by "The language of all strings starting with n-many a's or n-many c's followed by n-many b's" ...
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Implementing an efficent priority queue using only stacks

Is it possible to implement an efficient priority queue (as efficient as a heap) only using the stack data structure? The usual efficiency for a priority queue which is implemented using a heap is : ...
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Why are primitive types stored in a stack in systems level software?

Firstly 2 disclaimers, I am very new to the concept of a stack at a low level. I've only encountered it because I'm learning rust and the docs mention it. Secondly, I am aware of another similar ...
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Why do we do topological sorting to find shortest or longest path in weighted DAG?

I was wondering why do we need to do the topological sort before performing relaxing of edges. Wouldn't it'd be better if we do : if starting vertex is "s" ...
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190 views

Why postfix is used more often than prefix expression?

i was reading stack and i came across the infix, preifx and postfix expression.So i understood that why postfix /prefix expressions are preferred over infix expression ( due to its unambiguous nature) ...
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143 views

Priority Queue Using Stack

Can one build a priority queue using stacks, such that the priority queue has the same complexity for each operation. Could it be done? If so how? If not what is the best solution that can be done? ...
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When does kernel accessing virtual memory cause problems

I'm working with the CPU Pintos and have a question that is: In which situations can the kernel accessing the data in virtual memory via a pointer lead to problems? And how do you avoid them? I know ...
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Is call stack compile time or runtime detail?

I'm sorry if the question is quite naive, but I don't understand if a call stack is a language implementation detail or it depends on OS? What I'm trying to understand is what decides how to store ...
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Stack Permutation Algorithm

I was recently designing a Forth stack machine. I have an atomic instruction which rotates the top N elements. For example if the top of the stack is on the left, then say the N=3 rotate instruction ...
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Can a programming language be designed to use a fixed amount of memory?

I have been toying around with the idea of creating a programming language as a side-project, specifically trying to get extreme performance out of a machine. I have been thinking about the ...
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Implement heap using stack data structure

I want to implement a heap using the stack data structure. I have searched a lot on the internet. But I do not get any clue how to implement it. Can you please help me to implement a heap using the ...
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217 views

Minimum descending stacks

Assume a randomly ruffled pack of n cards with numbers from 1 to n. Each time we pick the top card from the pack (while there are still cards) and we put them according to the following rules: The ...
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Manage event programming under a stack-oriented language

I wonder how events, or more broadly reactive programming, could be managed in a simple stack-oriented language. For example, let's imagine a context where there is a button that displays a small ...
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Is it theoretically possible to dynamically grow array size in stack memory?

I was wondering, given the usual stack memory functioning, whether it is possible for an array like primitive type allowed to grow in size to exist. The functioning of such primitive type is as ...
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Generate all permutations of 1 to n with i stacks

Assume we have i stacks. the possible actions are: push to first stack form input pop from stack i and push it to stack i+1 pop from last stack to output If we have numbers of 1 to n starting from 1 ...
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Formal semantics of a mutable/imperative stack

When introducing formal semantics for data structures, immutable stacks are a nice simple example : $\mathit{is\_empty}(\mathit{create()})=\mathrm{True}$ $\mathit{is\_empty}(\mathit{push}(e, s))=\...
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284 views

Implementing a symbol table with a hash table and a stack

I was in class today, in a Language Translations course, thinking about the best way to write a symbol table for a compiler. My professor showed us a hash-table with linked-lists connecting different ...
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Multiple post-fix expressions for an in-fix expression

Today I was learning to convert post-fix expressions to in-fix expressions and vice versa. What I want to know is whether a post-fix expression can have more than one infix representations. For ...
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kPDA handling multiple epsilon transtions

I'm assigned to build a kPDA with 2 stacks that handles {w#w, where w is a string of (0,1)*}. I understand the # delineates the two strings, but I'm unsure of the logic when popping off stacks with ...
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228 views

Amortized time complexity for double stack emulated queue

Assume that we have a data type $stack$ which has two operation $push$ and $pop$, both operations' time complexity is $O(1)$ in worst case. The $stack$ also has a property $size$ indicate how many ...
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Merging balls interview problem

Here is an interview problem about balls rolling towards buckets from Sprinklr Interview Experience at GeekforGeeks. You are given $n$ balls on the table and all the balls are rolling towards the ...
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1answer
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Binary trees and preallocated nodes

I want to design a binary tree with preallocated nodes, in order to avoid calling malloc/free every time I want to insert/delete a node. The problem is I don't know ahead of time how many nodes the ...
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Can such an operation be done with two stacks?

Assume a Forth-like environment with two stacks, a main one and an auxiliary one. The following operations can be done on the main stack: DUP (duplicate the top ...
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Converting an infix expression to postfix

So the question is to convert the following expression to postfix: (a+b)^(p+q)^(r*s*t) The answer I get when I calculate is: ...
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108 views

Direct addressing on a huge array

A Question from CLRS book: (CLRS 11.1-4) We wish to implement a dictionary by using direct addressing on a huge array. At the start, the array entries may contain garbage, and initializing the ...
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395 views

What is the algorithm to determine valid push and pop sequences for stack when repetition of numbers are allowed?

Unlike traditional problems dealing with push and pop sequences of distinct numbers, I would like to know the procedure to determine the validity of the stack operations for sequences of non-distinct ...
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376 views

How to determine maximum stack size of LL(1) parser?

I am generating an LL(1) parser generator for LL(1) grammars that have a maximum stack size when executed in the table-driven parser. Specifically, I'm parsing HTTP headers using a parser generated by ...
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624 views

Can a processor without stack pointer registers, have a subroutine calls and interrupts?

Suppose a processor does not have any stack pointer registers, which of the following statements is true? It cannot have subroutine call instruction It cannot have nested subroutines call ...
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Why operating system needs interrupt stack, if it has process control block?

I'm reading about an operating system but some concept confuses me. What doesn't confuse me: When an interrupt or system call or processor exception occurs, it happens when user mode tries to ...
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How to keep track of changes done to concurrent stacks?

I am writing a small RPN calculator that works on some stacks concurrently. For example, if I have two functions: ...
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462 views

Maximizing the sum from m stacks using k pop's

Assume you have m stacks each some elements within it. If you are allowed to do k pops , the objective is to maximize the sum(sum increases by the value of the popped element). What is the best ...
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Is it possible for a stack-based programming language to be concurrent?

I have been reading about stack-based programming languages, such as FORTH and Cat, and it seems that given their nature, they can only execute one action at a time regardless of their paradigm (FORTH ...
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996 views

Sorting a stack using Bubble sort

How to sort a stack using bubble sort? Can use another stack if necessary.
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Why the overall architecture of Android OS is a stack and why not any other data structure?

The overall architecture of the Android OS is a Stack. What specifically justifies Stack to design the overall architecture of Android? Are all mobile OS like Windows Mobile, iPhone OS developed as ...
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Analysis of the Banana Game

My computer science professor introduced an interesting game in order to get us (his students) more familiar with the Stack and Queue ADTs. Game Description The banana game is played with a ...
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731 views

Data addresses with ADD instruction in various architectures?

How many data addresses are specified in an ADD instruction in accumulator based architecture, stack based architecture, and in the most common register-based ...
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Why is a sequence of n Push, Pop, Multipop operations O(n²)?

From "Introduction to Algorithms" by Cormen, Leiserson, Rivest, Stein, Third Edition, page 453: Let us analyze a sequence of $n$ Push, Pop, Multipop operations on an initially empty stack. The ...
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Minimum amount of swaps needed to sort a stack

Given a stack, what is the minimum amount of swaps needed to sort it? Since the bottom of it stays intact and we slowly move to the upper part of it, if the stack contains n elements, the amount of ...