# Questions tagged [vector]

A vector is a single-dimensional array: it contains components that can be accessed using an integral index. In some languages the size of a vector can grow or shrink as needed to accommodate adding and removing items after the Vector has been created. Use 'vector-graphics' for graphic display.

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### What should I do better in my vector implementation in C++?

I am starting to learn new features related to C++(templates, l-value, r-value, move, perfect forwarding, etc) and I decided to test what i learned so far by implementing my own vector class. I wanted ...

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21 views

### Assistance needed for a program to generate UML type draft of a code

I am trying to write a c++ program that prepares a draft indicating the classes(and their members), functions (and hopefully generate a UML diagram from it sometime). The first step that i identified ...

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7 views

### How to find the first index (row number) of an element in a 2d vector

We are assigned to make a checker program that takes two input files. The two files contains groupings of 30 students (10 rows and 3 columns) so there are 3 students per group. We need to check if ...

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67 views

### What is the difference between vector<int> a(60); and vector<int> a; without the indexind feature [on hold]

What is the difference between vector<int> a(60); and vector<int> a; except the indexind from 0?
EDIT: I want to know if vector<int> a(60); is better than vector<int> a; at ...

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48 views

### How to push structure vector into structure vector?

Does anyone know how to push structure vectors into structural vectors?
Question. I want to push_back Part_vec into Pallet_vec.
and cout code for checking.
Also i wonder if there is a common way to ...

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**1**answer

25 views

### Question about accessing object method with vector iterator

I am new to c++ and I have an assignement on vector/iterators. I ran into a problem that I was able to solve by searching on the internet but unfortunately the forums I visited only provided with the ...

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57 views

### Basic calculations of vectors in Python

I am writing code that uses calculations based on points of known positions (XYZ) and their velocity (vx, vy, vz). I'm trying to calculate the basic vector calculations for eg. length (L=sqrt(x ** 2+y ...

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62 views

### How to add an object to a vector and check if it worked

I got a class WayPoint that contains a pair of doubles and a name.
I got a class WayPointContainer that contains a vector of Waypoints.
WayPointContainer got a method to add a WayPoint to its vector ...

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29 views

### Converting data.frame to high-dimensional matrix

For example, consider the following data
> sample.df
f1 f2 x1 x2 x3
1 2 2 7.28 9.40 5.02
2 1 1 6.30 9.56 3.74
3 2 1 6.88 8.72 3.14
4 1 2 6.68 9.58 3.84
I wonder how to write MAGIC ...

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75 views

### Get a view to all T's in std::vector<std::tuple<Ts…>>

Imagine I have a container which is similar to std::vector<std::tuple<Ts...>>.
From that, I would like to get a "view" (non-copying) to all T's such that I can operate on that view as if ...

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**1**answer

31 views

### TypeError: Bad Operand Type for abs(): 'ReferenceFrame' but I have no abs() function

I'm trying calculate the curl of a vector with its del operator, and so I'm using the curl from sympy and just having the vector cross with the reference frame, but I get this error: what exactly am I ...

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61 views

### Linux much faster than Windows when reading data from .txt file and placing into vector. How would I speed up Windows to do the same?

I have .txt files for data (100MB - 700MB). When reading these files and placing them into vectors, Linux does this 20-30x faster. Is this a system issue, or is there something I can do to speed up ...

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53 views

### How do I return a reference to a concrete type that was added to a vector of trait objects?

In this code, I take a vector, create a struct instance, and add it to the vector boxed:
trait T {}
struct X {}
impl T for X {}
fn add_inst(vec: &mut Vec<Box<T>>) -> &X {
...

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**1**answer

35 views

### Split character vector by element in R?

Given a vector:
c("kuku", "pupu", "lilu","","ff","rrrr", "", "rrr")
How can I split it by ""?
To get 3 vectors:
c("kuku", "pupu", "lilu")
c("ff","rrrr")
c("rrr")

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17 views

### How to add each word in a sentence of string into vector [duplicate]

Which word appears most in the sentence
For example:
Apple pen banana pen banana banana pen
Output:
banana pen
Because the two words appear most (3 times).
So I want to put every word in ...

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33 views

### Replacement of cycles with algorhitms- something goes wrong and I can't understand what am I doing not well

I have a project for the university with three classes and I have a little problem. The program I wrote works, but they told me I have to use algorhitms somewhere and not only for cycles for the maps ...

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**1**answer

40 views

### Problem with add method vector of 2D-array in java

I have declared a vector of 2D-array in java. At each step I add an array into vector by add() method. But when print out this vector to see what inside, I've got an unexpected output. None of these ...

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**2**answers

31 views

### input into vector without pre_defined length…? [on hold]

Suppose, i want to add all the elements in the vector and want to print the result out. the number of elements that i want to enter is not fixed.
let the input be:
3
5 2 8 5
34 64 23 10 8 12 5 4
95 ...

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**1**answer

23 views

### concatenate two vector from another vector

I have a vector and in every story, I have a vector where are all the string of my story. I need to verify if two stories have the same name and after that concatenate them.
histoire is story
titre ...

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**1**answer

28 views

### Dot product between scipy sparse matrix and numpy array give ValueError

I'm trying to calculate the dot product between a scipy parse matrix and a numpy array.
First I was using a numpy matrix, which you can see in the following code:
def power_iteration(matrix, n):
...

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35 views

### How to share array of vector between classes

I would like to get an array of vectors from a class to use it in a separate source file.
I had no luck with an array of boolean neither.
I have tried to get it through a public method.
It works with ...

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34 views

### How to cout a function that returns a vector of strings?

To cout a vector of strings is easy, iterate through the vector array.
But what if a function returns an array? Is there any way to directly cout the return of the fuction?
Otherwise I think I have ...

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**1**answer

54 views

### Symmetric Matrix in C++

Checking whether a 2D Matrix is symmetric or not
Task is to output YES if the matrix is symmetric else output NO.
I am not getting the expected result. Can someone please help me out and please let ...

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70 views

### After the function finished, Why an vector cause the free() error?

I write some codes to calculate the inverse dynamics. It seems that the function IverseDynamicscalculation is finished and return true. Then error occurs: free(): invalid next size (fast): I know ...

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**1**answer

29 views

### Vectors pointers with vector slices for Tree generation from preorder and inorder vectors

I'm getting the following error:
solution.cpp: In member function buildTree
Line 26: Char 62: error: no matching function for call to 'Solution::buildTree(__gnu_cxx::__alloc_traits, int>::value_type*...

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**1**answer

28 views

### Iterating over const_iterator

ALL,
I have a function with the following signature:
void foo(const std::vector<Bar *> &myvec);
Inside this function I need to loop thru the members of the vector and perform some ...

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38 views

### Unsure as to how I get the position of a Texture in SDL from within its class?

Im unsure as to how I get and set the position of a texture once its been rendered onto the screen. Im using SDL and have set up the character class and its relevant header file however how I go about ...

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16 views

### TypeError for a non-numerical vector, and to do the curl

So I'm trying to solve a problem for a class, and I'm trying to do the curl, but it's in variables. I end up getting a TypeError: 'type' object is not subscriptable. I don't know what I'm doing wrong, ...

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49 views

### How to copy content from a file into a 2D vector? (C++)

I have a sort of map made out of numbers in a file. I want to read all of it into a 2D vector I created inside a function for it.
I have initialized the vectors in 0s.
What happens is when I compile ...

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**1**answer

41 views

### Place objects based on coordinates, not on the central coordinates in Unity

I'm creating mesh objects dynamically based on the screen.
So objects that contain mesh objects are always the same size, but mesh objects have different shapes and sizes.
I want you to see my ...

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51 views

### Is it possible to include vector fields in a protobuf message to generate Rust struct?

I have a protobuf file used to generate types in a project. One of the types looks like:
syntax = "proto3";
// ...
message myStruct {
int32 obj_id = 1;
string obj_code = 2;
string ...

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20 views

### Erroneous vector filtering from image based on direction (directional filter)

I am working on the motion estimates using two images by python based algorithm. I got the attached vector field (green color). This field includes some erroneous vector. I want to filter those ...

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44 views

### What function should I use to return a vector of characters?

So I have a data set that looks like this:
gene_id gene_symbol Chr Biotype L001P L003P L004P L005P L008P L010P L012P L014P L016P L017P
2 ENSG00000000003 ...

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88 views

### convert a byte vector into a vector of floats

I'm sending a fixed length byte stream over a serial port to another computer and I'd like to try and convert the byte stream to a vector of floating point numbers.
My stream has a delimiter stop ...

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35 views

### Why does My Program Not Exit a While Loop that Erases a Vector Position at The End

I'm making a program that sums hexadecimal numbers up to any amount of characters and in the function sumHexArray, the while loop for some reason doesn't exit correctly, and I do not know why.
The ...

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**1**answer

43 views

### Member vector not maintaining elements when attempting to push from member function

I have a static member function that initializes an Object1, which contains a member vector of a Object2's. Object2 has a member vector of strings.
I am trying to add a series of strings to Object2's ...

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**1**answer

42 views

### Error in multiplying matrix vector - invalid operands to binary * (have 'double *' and 'double *')

I'm trying to multiply a large and random matrix (NxN) and a random vector (N), using pointers.
Why am i getting an error type "invalid operands to binary * (have 'double *' and 'double *')" ?
The ...

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57 views

### Can we use vector in c++ to take user input of unknown size only till we hit enter?

I was trying to take user input in a vector in c++, as vector is a dynamic data structure i wanted it to take input as long as user wants and when the user hit enter key it should stop taking the ...

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47 views

### Runtime error when using push_back() on smart pointer to vector

I am trying to fill a vector, by dereferencing a smart-pointer. During runtime the program crashes after one iteration of the first "for" loop used for entering the variable input.
using namespace ...

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28 views

### How do I return a Generic Vector Iterator from an Inline Template method?

OK. As the question states I have an Inline Template method that returns an Iterator to a generic vector.
note: I know I should change the implementation to std::find, but that's not the problem I'm ...

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21 views

### How can i erase element of VECTOR LIST in c++?

I need to erase the element of position 'k' in my code , Suppose i got the '3' in K so i wants to erase member of position 3 in vector list . What is the solution?
thanks in advance !
using namespace ...

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33 views

### output a collection of collections using templated operator<<

I want to output a collection of collection (a vector of vectors in this case) by calling the outside collection once by operator<<
It works when I remove the ' ' from the operator<<() ...

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17 views

### How to run a regression with dates and variables (each variable linked to a stock)?

I am trying to run a regression with dates (lines) and variables (columns).
My problem: We haeve 60 stocks and for each of them 5 variables.
It is the same variables for each stocks but I have more ...

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2k views

### Performance gap between vector<bool> and array

I was trying to solve a coding problem in C++ which counts the number of prime numbers less than a non-negative number n.
So I first came up with some code:
int countPrimes(int n) {
vector<...

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69 views

### strange memory behave of resize and reserve about vector

I know reserve(n) only allocate n space but size is zero.
while resize(n) allocate n space and size is n.
but when I observe the memory change by window task manager in the test , I'm confused by ...

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44 views

### How do i overload operator “[]” for vector containing my own class objects

So i got a class WayPoint (inside the namespace HHN).
And i got a class WayPointContainer.
The container got a private vector variable to store objects from the type "HHN::WayPoint"
What i want to ...

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**1**answer

42 views

### How to compute a probability matrix based on a binary matrix?

My attempt is:
library(igraph)
set.seed(41)
n<-10
A <- sample.int (2, n*n, TRUE)-1L; dim(A) <- c(n,n);
m <- sum(A)
g <- graph_from_adjacency_matrix(A)
k_in <- degree(g, v = V(...

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63 views

### how to input structural type vector data into structural vector member (nested structural vector) in c++

I'm beginner and implementing scheduling simulation.
I want to insert the structural vector(Order) into the structural member vector(selectedParts) in the Pallet.
I know how to insert the int type ...

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**1**answer

39 views

### search in record set / update value

I created a record set using structs, vector and added couple of records. This is the code that does it. This should run as is - on an Arduino/ESP8266/ESP32.
#include <string>
#include <...

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57 views

### Accessing an uninitialized value, most probably in a vector

I am doing an exercise where I need to find a positive integers p and q which are factors of another natural number n.
Following the formula n=pq*q where p is a squarefree number.
However, for some ...