I am trying to pop the element on a vector off and return its value at the same time
vector.push_back();
Unfortunately that code only removes that element from the vector it does not return it
Is the only way to get the element and destroy it is to do this?
vector.back();
vector.pop_back();
I have a vector of int,
Code:
vector<int> row_numbers{1,2,3,4,5,6,7,8,9};
I want to sequentially remove one element at a time starting with the first. When the second element is removed, the first element needs to go back in. The sequence would look like
Code:
// original vector, row_numbers.size()=9
row_numbers{1,2,3,4,5,6,7,8,9};
// trimmed vector, row_numbers_trim.size()=8
[Code] .......
I have been working under the assumption that the best method would be to have row_numbers remain untouched and work on a copy. For each step in the sequence, you would create row_numbers_trim as a copy of row_numbers, and then remove an element from row_numbers_trim.
Code:
// position being removed
int counter = 0;
// copy original vector
row_numbers_trim = row_numbers;
// remove the first element from the copy
row_numbers_trim(row_numbers_trim.begin()+counter);
All you would have to do here is to increment counter in a loop. is there a better way?
I have a cpp app that reads in a number of files and writes revised output. The app doesn't seem to be able to open a file with a ' in the file name, such as,
N,N'-dimethylethylenediamine.mol
This is the function that opens the file :
Code:
// opens mol file, reads in rows to string vector and returns vector
vector<string> get_mol_file(string& filePath) {
vector<string> mol_file;
string new_mol_line;
// create an input stream and open the mol file
ifstream read_mol_input;
read_mol_input.open( filePath.c_str() );
[Code] ....
The path to the file is passed as a cpp string and the c version is used to open the file. Do I need to handle this as a special case? It is possible that there could be " as well, parenthesis, etc.
question from chapter 11, qn 8 modern C programming by king
Write the following function: Code: int *find_largest(int a[], int n); When passed an array a of length n, the function will return a pointer to the array's largest element
Code:
#include <stdio.h>
int *find_largest(int a[], int n)
{
int i, x;
x = 0;
[Code].....
have traced the code line by line and it prints correctly up to line 31. However, when the program exits (line 35) , it goes to some other screen with very complex code and my output disappears.
Just to clarify: If I just run the code as is, there is no output. However, when I trace the code line by line, the output appears, but then disappears as the program exits My input was 1 2 3 4 5 6
I have a program where I roll a die X number of times and need to print how many times it lands on each side. I tried to create an array in the class aDie that increments each time the corresponding number is rolled but when I go to call and print it in the main my out put is 0. I just picked how many times it landed on the side 4 just to see if it works and it doesn't.
#define ADIE_H
#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>
using namespace std;
class aDie {
[Code] .....
I am trying to write a function to return the first element of a link list queue. I am not real sure how to implement this. I have include a copy of the struct for my Node & queue.
Code:
typedef struct event_Node {
void *data;
double arri_time;
double serv_time;
double depart_time;
double start_o_serv;
[Code]...
I am storing info in a vector but I want to store certain info at a particular index. I am new to using vectors and am unsure about have to do this. I am aware of the insert method but am confused on how to use it to store at a particular index.
View 1 Replies View RelatedHow to access an element of the point3f vector. E.g. :
int main() {
vector<Point3f> a;
a.push_back(Point3f(0,0,0);
a.push_back(Point3f(0,0,1);
//print first x,y,z element
cout<<a[0]<<endl;
[Code] ...
But it doesn't work firstly because it says can't use typename i.e. <float>
pop_back just returns void, so I just can't use that?
erase is okay but it doesn't return anything....
Do I use a combination of both?
I was instructed to write a binary search function which would return true if an element, inputted by the user, was found in the array, and false if it was not. I'm not sure why, but my function always returns false. My code is as follows.
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
//binary search function
bool search (int array[], int item)
[Code] ....
Why my code does not fulfill it's purpose???
I have a fun question that is an end of an inherited class. I am trying to return the day of the week using time structures. However, I cannot get the correct date from two different structures, even if they are declared as different structures. So, when I check the number of the week, the two provided to check with are the same.
point is: They keep coming up as the same.
bool Weekly::occurs_on(int year, int month, int day) {
struct tm * chec ;
time_t clock1 ;
time(&clock1);
[code]....
How could I search a vector element with multiple strings
i.e. vector.at(i) = This is a test
How could I search that to look for the word "test" in that element?
Consider I have a vector of strings and then I use an istringstream to read each word of each element in the vector, why do I nescessarily use an istringstream?
This is the code that does what I just described (I think)..
Code:
for(auto &elem : svec) {
istringstream strm(elem);
while (strm >> word)
//Magic
}
What would be the equivalent of using something else than an istringstream in this scenario and how does the istringstream work?
I am programming a 2-D platformer video game. The stages are composed of an array (really a vector) of 16x16 px^2 tiles. I have defined a base class "Tile" and several derived classes, e.g., "Ramp", "Door", etc., which have their own attributes. The idea is that upon entering a room, the program will load all of the necessary tile data for that room into a vector. So, I have a vector that looks like: vector <Tile*> room_tiles, and resize it based on the total number of tiles in the room: room_tiles.resize(Tile_Count). I then want to read in certain info from the data file containing all of the tile information for that room. For example, if the data file says Tile 5 should be a ramp, I want to change the 5th element of the room_tiles vector to the derived ramp class. This is really where I'm having trouble. I've worked with vectors of base and derived classes before, but those were always of indeterminate size and I always used something like: (Vector).push_back(new DerivedClass()) to specify the derived class of that element. The problem is that that method only seems to work if you are appending elements to the end of a vector.
how I can do this?
I'm having a problem filling a vector from a file. Basically, it is adding an empty element at the end. I'm new to Qt and haven't worked with file streams much so how to stop the stream before it adds the extra element.
void gui::get_data() {
mileage.clear();
QFile file(file_label->text() + ".txt");
QTextStream in(& file);
float m;
float g;
QString d;
[Code] ....
But, if I add another element to the vector and write that the file look like this.
//file after adding element
132654 0 02132014
132654 0 02132014
0 0
132998 22 02202014
I have it set to append at the moment so that is why the first line is repeated. I figure the problem is with if(in.atEnd()). I could fix it by deleting the last element right after adding it, but that seems like more of a hack than anything else.
I have N vectors which look like this:
[1→m] [m+1→2m] [2m+1→3m] [3m+1→4m] [4m+1→5m]..... [{(N-1)m}+1→Nm]
I want to select 1 element from each vector without duplication of any combinations. Essentially only when all combinations are done with 1st element in first vector ,only then it should move to next element in first vector.
Say i have elements :[123] [456] [789]
my combinations should be like
147
148
149
157
158
159
167
168
169
247....
Also, I cant have any repetitions and only after all combinations of 1 are done only then the loop has to move to next combination ie 247 combination and so on.
I tried NCK (n choose k) command but it gave me random combinations. How should i go about it with using minimal for loops?
Ok here is the code
//assuming that all the directives have been included here
void ptrPointer(vector<string>* const p, int n);
int main() {
vector<string> inventory;
vector.push_back("sword");
vector.push_back("knife");
[Code] .....
Well...my question is how come the last statement or cout statement to be accurate won't work and display? Since we can do something like this below?
string text = "some text";
string *p = &text;
cout << p;
I passed the address of the vector to the function. And then display the address. It is a pretty common operation. But it just won't work. But then we do something simple similar to that of the vector. But it works.
My function has the following prototype:
std::vector<double> calculate_mag_response(double start_freq, double end_freq,
int N, std::vector<double> num, std::vector<double> den
The function should return a vector size N of magnitude responses in decibels of the transfer function defined by numerator and denominator vectors num and den. To adequately test, you should drive this with more transfer functions.
#include <vector>
#include <iostream>
#include <cstdlib>
#include <ifstream>
using namespace std;
int main(int argc,char *argv[]) {
vector<double> myNum, myDen, results;
[Code] ....
I have a pretty big std::vector<matrix>, where matrix is a custom class defined by me. I would like to know how much memory has been allocated to that vector at a certain point in time. Is there any way of doing this in c++?
Or is my only shot, taking a look at the task monitor of windows/unix/whatever at execution time to estimate this?
So I have a Binary Tree and I need to return a vector of integers (the nodes) of the heaviest path in the tree.
First, is it possible to do in C? Because I think a vector is an ADT in C++.
I've started writing something recursive, which worked for a balanced tree of height 1, and failed for longer height.
This is what I've written - [URL] ....
The error is unclear but suggests Its received a bad pointer from another heap. It references dbgheap.c line 1322 and assertion failure
I have two string vector functions the first is called from the main function, the second is called from the first.
Their purpose is to receive a string of text and numbers in a semi-specific format, which the main body of the code reads from a text file, and delaminates the data as to return the first variable in the string as the variable name and the second as the variable value. Along the way it filters out a lot of the unwanted whitespace and punctuation.
E.g "{ VariableNameA 123 }" would be returned as "VariableNameA" And "123"
The code works perfectly for most of the lines in the text file but fails on one particular line where the first variable is 25 characters long. Basically it works for anything 22 characters or less. There are never more than 4 elements in the vector and each element is never intended to be longer than 25 characters.
It fails trying to return from the second split function to the first split function.
Is there a limit to the size of each vector element? I'm struggling to find a way round this without having to rewrite the whole thing.
vector<string> split(const string &s, char delim) {
vector<string> elems;
split(s, delim, elems);
return elems;
[Code] ....
Okay, so for an assignment I need to write a function called find() that returns a reference to a vector. So I have vector <int> & find(string & key); If I do this, I get the obvious warning warning: reference to local variable 'lineNum' returned [enabled by default].
If I do vector<int> & find(string & key) const; I get a huge error that starts out like
In member function 'std::vector<int>& index_table::find(std::string&) const':
indextable.cpp:74:30: error: no match for 'operator='
Am I using the const identifier incorrectly?
How to pass my array to the function and return it as a sorted vector. I'm kind of lost with the functions part.
Problem: Write a program that performs a sorting routine as discussed in class. Create an array of 10 integers (e.g., 63, 42, 27, 111, 55, 14, 66, 9, 75, 87). Pass this array to a separate function that sorts the integers and returns a vector containing the sorted integers. Use either the SELECTIONSORT algorithm or the INSERTIONSORT.
Code so far:
#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <iomanip>
[Code]...
So I have linked list and function which deletes element if next element is bigger, so my code is working but its not working with first element, in the comment I have wrote code which I would code for checking that first element, but when ever I check it is blowing up all program.
#include <iostream>
using namespace std;
struct llist {
int x;
llist *next;
[Code] .....
I have a global list that contains smaller lists of char arrays. I have an issue where when I'm reading back the inner lists the last element of one list seems to point to first element of the next.
So my data looks like the below (values separated by commas with the pairs separated by tabs. The last pair in a line is the same as the first). When I read the first list back instead of seeing "456.678,678.98" as the last element in the list. I see "435.67,234.98" twice: at the end of the first list and start of the other. I have debugged when the list is populated and can see the correct values going in so I can't figure what's happening.
456.678,678.98 123.45,345.56 256.67,789.98 456.678,678.98
435.67,234.98 123.65,342.56 987.78,678.34 435.67,234.98
Code to fill the list:
obstacle_list = op_prg_list_create();
while (fgets(line, sizeof(line), obstaclePositions_traj_file) ) {
token = strtok(line, "
"); //Pull the string apart into tokens using the
input = op_prg_list_create();
[Code] ....
I have an std list of type double.. and the list is always guaranteed to have just 2 elements. I need to get the value of element 2 minus element 1. What is the least amount of code to accomplish that?
I tried this:
Code:
list<double> dList;
dList.push_back(1.0);
dList.push_back(2.0);
list<double>::iterator iter = dList.begin();
list<double>::iterator iter2 = dList.end();
double result = *iter2 - *iter;
But this code does not work. Why not?
