Questions tagged [c++]

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How to get next array in kmp algorithm?

Here is the code to get next array in kmp algorithm, please tell me how len = lps[len - 1]works. It is really hard to understand. Consider the example ...
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What is `const = 0` at the end of function declaration [closed]

I was studying the c++ code is written in https://github.com/OpenSourceRisk/Engine/blob/master/OREData/ored/utilities/indexparser.cpp#L197 There is a line of code - ...
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1answer
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Cancellation in C++

I am trying to figure out what the problem with the following expression in C++ is: y=std::log(std::cosh(x)); My first intention was that there might occure a ...
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1answer
66 views

Math behind leetcode problem 47 permutations II

Please tell me why the expression i>0 && nums[i] == nums[i-1] && !used[i-1] works on getting unique permutations. And what is the math behind it? ...
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4answers
77 views

How do compilers assure stability?

Suppose you need a c compiler. It would be preferable to write that compiler in a c-like language, given the complexity of a compiler of that degree. At best, the c compiler would be written in c, but ...
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1answer
49 views

What is the difference between python list and c++ vector?

I read about the similarities between the python list and c++ vector and it looks as if the only difference is python list is heterogeneous. Are there any other differences? How are they both ...
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2answers
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Analyzing space complexity of passing data to function by reference

I have some difficulties with understanding the space complexity of the following algorithm. I've solved this problem subsets on leetcode. I understand why solutions' space complexity would be O(N * 2^...
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1answer
61 views

C++ STL: How does the distance() method work for a set/ multiset (stored internally as a self balancing tree)?

I'm working on the problem: Count smaller elements on right side using Set in C++ STL The solution is to add each element to the set and then to count the elements on the left, the distance function ...
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2answers
88 views

Efficient way to reduce a binomial coefficient as a fraction

Here is the full problem. You need to calculate Euler's totient function of a binomial coefficient $C_n^k$. Input The first line contains two integers: $n$ and $k$ $(0 \le k \le n \le 500000)$. ...
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1answer
58 views

find shortest paths from source to all vertices using Dijkstra’s Algorithm?

For Dijkstra’s,i can find shortest paths from source to all vertices in the given graph but how can i calling the algorithm |V| times taking each vertex as a source and store all tables ??? For ...
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2answers
53 views

Understanding memory leaks in C/C++ [closed]

I was looking at an example here: https://blog.parasoft.com/finding-memory-leaks-in-c ...
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0answers
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parallelized data structure

I'm searching a data structure that supports O(1) concurrent insertions (thread number is known in advance) and iteration over its elements (insertion order doesn't need to be preserved). While one ...
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3answers
83 views

Why do we need value-returning functions?

I'm just a beginner at C++ programming. I am currently having hard time grasping the usage of value returning function and non-value returning function. Void functions are called non-value returning ...
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1answer
27 views

How will I calculate the time and space complexity for this pyramid algo? [duplicate]

This is an algo. programmed for displaying a letter pyramid if the buildPyramids() method is passed argument str, i.e. "12345": ...
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How to Tokenize a String and Save Each Substring Separately (Independent Names for Each Substring)

I am given two files one with the name of person and the location that they are from (Evan Lloyd|Brownsville) and one with the name and salary (Evan Lloyd|58697) (the line number that you find the ...
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2answers
63 views

Is this a misleading or undesirable implementation of a hash map?

I read a C++ implementation of a hash map here. https://www.geeksforgeeks.org/implementing-hash-table-open-addressing-linear-probing-cpp/ Let's say key k1 has a ...
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1answer
19 views

Recursive Call Inside Argument List (C++) [closed]

So, my professor asked me to implement recursion in different ways to compute $a^n$ (a and n being integers) and rank them according to their space efficiency. Now, here is one of the methods I came ...
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4answers
170 views

How do you find a hash function that respects a custom equality function?

I've been tasked with hashing arbitrary types in C++, with the caveat that A == B implies hash(A) == hash(B) even if equality of ...
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2answers
47 views

Find first occurence of multiple tokens using C++ [closed]

I am using C++03. I have a stream of chars and I need to find the first token from a group of tokens. That is, I need to find the lowest indexed match. Specifically, the stream is just an char array, ...
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1answer
156 views

Why are struct and class essentially the same in C++?

struct and class in C++ are nearly identical (as covered for example here). But why is this so? What did happen when C++ was ...
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1answer
146 views

Halting problem in C++

The halting problem relies on the fluidity of Turing machines. That is, a string can represent a machine. Can you do the same for C++ on a modern computer? Let's see my first attempt. Let ...
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1answer
137 views

numerically stable log1pexp calculation

What are good approximations for computing log1pexp for single precision and double precision floating point numbers? Note: ...
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1answer
142 views

Linked list: advantages of preventing movement of nodes and invalidating iterators on add/remove

C++ and Java include native classes for linked lists, C++ std::list and Java LinkedList For C++ std::list, nodes can be "moved" within a list, or from list to list (if the lists are compatible), via ...
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0answers
31 views

How to justify using available code (in different language) for comparing algorithms [closed]

I have proposed an algorithm for a scheduling problem in a submitting paper. In the revision, the reviewer asked us to compare with another algorithm in the literature. Our algorithm is in MATLAB, and ...
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0answers
98 views

Given n strings, how to output their order after k phases of the radix sort (huge constraints)?

Disclaimer This is not from an ongoing contest, this is from my course of ITMO on edx.org, which is a paid code so I cannot give you a direct link to the course. Problem You are given $\...
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1answer
61 views

How does C++'s type checking work when passing overloaded or templated functions as parameter

As I understand, C++ in general features 'one-way' type checking. That is checking the sub-expressions and get their types, and see if the types so far satisfy the constraints imposed by the current ...
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1answer
239 views

Complete the following table by specifying the scope of each declaration

I'm having a hard time understanding this question. Can each declaration have more than one scope or can a declaration have more than one scope? If it's the later it would be: Declaration ...
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1answer
632 views

Where are C++ templates inside of the lambda cube?

C++ templates have type variables and can express lambdas, so they must have System F embedded. But is that exactly where they are located in the lambda cube? Can C++ templates produce new types or ...
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0answers
84 views

Summary of types of equivalence and equality in type theory, with notations and examples

Coming from non-computer science background, I am trying to understand the different types of equivalence and equality usually used in type theory. Ideally, I am looking for clear definitions and ...
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2answers
64 views

Compare each array $i$ member to all array $j$ member where $(i > j)$ , in time less than $O(n^2)$

I am new to algorithms so sorry to ask simple question I am working on a problem which is about array of integers, my solution is right but not good enough, because I have time exceeded exception on ...
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0answers
76 views

Implementing a linear programming feasibility test in 3D

I have a little problem which requires determining if a system of linear inequalities in 3D is infeasible. The constraints (or oriented planes) are added one by one, so there is an opportunity to stop ...
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1answer
654 views

Bytes from integer using bitwise operators

So I am extremely confused with using bitwise shifts used to extract the bytes from an integer. I find that if I do something like this... ...
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1answer
171 views

How to count number of 1s of the first k positions in a bitset (bitmap)?

Input: Given a bitset $b$, which is is an array of 0s and 1s, of length $L$, and a positive integer $k$. Output: the total number of 1s in the first $k$ position of $b$. Obviously it can be done in $...
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0answers
80 views

Generate an AST from an indefinite grammar and logic

As said in the title, I have to generate an AST from a grammar and logic (or a"syntax" if you prefer). This grammar and syntax are both indefinite in the program, meaning that it is the user (a ...
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1answer
44 views

How is ReLU used in machine learning functions

I've seen how sigmoid would be used in machine learning sigmoid(dot(activations, weights)-bias) like this ^ but sigmoid makes sure your values are between 0 and ...
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0answers
1k views

To find median of k sorted arrays of n elements each in less than O(n*k*log(k))

How to find median of k sorted arrays each of length n? Note that total elements would be n*k. I know it can be done in O(n*k*log(k)) using merge technique. I am looking for a better time efficient ...
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1answer
282 views

Why isn't deque implemented as a dynamic array?

We know that std::vector in C++ is implemented as a dynamic array with specific pattern of reallocation (multiplying capacity by a constant), which allows it to ...
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1answer
392 views

Find maximum non contiguous subarray that respect a specific rule [closed]

Given these two arrays: [5, 3, 4, 1, 2] [1, 3, 2, 4, 5] Find the maximum subsequence in both arrays that the index of the elements are in a crescent order: ...
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1answer
520 views

Find Length of longest substring with all 1's in a binary string with k queries

Given a string of size n consisting of 0s and/or 1s.you have to perform k queries and there are two types of queries possible. "1"(without quotes): Print length of the longest substring with all '1'. ...
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1answer
50 views

What operation is the algorithm performing? [closed]

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1answer
88 views

Print maximum frequency number in an array(with slight modification)

There is an integer array and 2 variables Q and M.The output required is the number which has the maximum frequency in the array, but the catch is that each number in the array can be increased/...
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2answers
109 views

How do compilers implement symbolic (rather than textual) insertion?

From a programming language designer's point of view, how is "symbolic" insertion implemented as opposed to "textual" insertion using pre-processor macros? I understand the basics of how "textual" ...
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1answer
251 views

What type of function is main()?

As the functions are of 2 type:1.Pre-defined/library functions,2.User defined functions. What type of function is main() function? This doubt comes in my mind while writing a program we define the ...