Names are std::string no more than 3 characters in length. What built in container or boost container is fastest at finding a name (Key) in it's container.
Finding a name.
At the name will be a value double.
I need the most efficient at finding and finding/updating the value. Forget out inserts and deletes.
Suppose you have defined a container of elements and you want do define a comparison function between elements based on the ordering of the elements in that container. What algorithm for the comparison would be the most efficient?
Example:
master = {tom, sam, mary, sally, bert, frank}
subset = {bert, sam, mary, tom}
goal: change subset to {tom, sam, mary, bert}
My current idea is to simply iterate from the beginning of the container, and whichever of the two elements is found first is the lesser (assuming the second is not the same as the first). It seems kind of naïve though. Any better performing algorithm? This is what I have so far:
#include <iostream>
#include <iterator>
#include <list>
#include <vector>
#include <stdexcept>
#include <algorithm>
[code]....
Would perhaps forcing the container to have a random access iterator, like vector, and then writing a specialized comparison function based on that perform even faster? Or perhaps force the container to be a map to integers, and compare the elements by comparing the integer mapped values?
#include <iostream>
#include <string>
std::ostream& operator<<(std::ostream& os, const std::string& str) {
os << '[';
[Code].....
In the above program, I define an operator<< function in global namespace which has exactly the same signature as the one define in <string> header : [URL] . In the main function, I call operator<< on cout and a string, after which I guess it would cause ambiguity. The result is out of my anticipation, it compiles and prints [hi]. So I guess my function is a better match because it does not require argument-dependent lookup (ADL). Moreover, even if I add using namespace std; at the beginning of the main function, the program still compiles and prints [hi].
In short, I have two question:
#1 : Why is my function a better match (therefore no ambiguity) in the two cases respectively (with and without using namespace std;)?
#2 : Does using namespace affect ADL? Is ADL still performed after applying using namespace, or is it not performed because the function is thrown into global namespace?
Write a template that accepts an argument and returns its absolute value. The absolute entered by the user, then return the total. The argument sent into the function should be the number of values the function is to read. Test the template in a simple driver program that sends values of various types as arguments and displays the results.
#include <iostream>
using namespace std;
template <class integertemplate>
integertemplate totalint (integertemplate integers) {
cout << "How many integer values do you wish to total? ";
cin >> integers;
[Code] .....
I am trying to open a file and print the contents of the file to the terminal window. It works when I put the file right in the directory with the Solution but not if the file is out on my desktop and I use the full path. Here is the code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int OpenFile(){
fstream SampleFile;
[Code] .....
What is the most efficient way to calculate Fibonacci. Is it recursion with memorization, is it iteration or is there another approach?
View 1 Replies View RelatedI have to write a function
struct rNumber add(rNumber a ,rNumber b);
which adds two rational numbers in following representation :
rNumber := s*(n/d)* 2^e
struct rNumber{
_byte_t s; // sign (do not consider for this question)
uint n; //numerator
uint d;// denominator
short e;//exponent
}
If the exponents of both numbers are not equal, then they have to be made equal in order to add them. This can be made in 4 ways : increase or decrease the n or d of both numbers.
But if we decrease the denominator of a number (a.d =1) by shifting it for example 1 bit to the right, we get 0 which leads to INFINITY for the fraction. In another case decreasing the numerator would lead the n to be 0 which meanse the whole fraction is then 0.
According to this, in worst case, all 4 cases has to be checked for the right result.
So far the UNDERFLOW of n or d is considered. If we try to increase the value of n or d, then OVERFLOW may also occur.
The very first, intuitive solution would be iteratively increase/decrease one of the terms and to check if the change leads to ZERO or INFINITY.
i have a vector of stores. i would like to delete the specified choice(store) from the list. Here is what i have but my erase statement is wrong and wont compile.
void Store::deleteSpecifiedStoreFromList(string choice) {
for (int i = 0; i < this->stores.size(); i++) {
if(this->stores[i].getStoreNames() == choice) {
this->stores.erase( std::remove_if( this->stores.begin(), this->stores.end(), choice ), this->stores.end() );
}
}
}
I'm currently building a new data structures that will be used in monte carlo generators (and so will be constructed several million times) and I'm wondering what's the best way (computer-speed-wise) to pass the data to the constructor. I am currently doing it using references and passing arrays as pointers like this:
Code:
class particle{
public:
particle(double *ar,int &id):IDup(id){
for (int i=0;i<5;++i)
Pup[i]=ar[i];
}
int IDup;
double Pup[5];
};
I'm assuming that since using references has no need to create a temporary memory slot it's more efficient .....
As for the arrays: is there a way for me to pass them as reference as well? (not using c++11), I'm using arrays instead of vectors as much as I can because I assume that vectors, being more advanced data structures, would take more time to create.
I'll process the raw content of a stream which obviously will be loaded one chunk at a time into an buffer.I need to check if every chunk content is x00 filled. If it is, I'll increase the blank chunks counter of 1.On your personal opinion, which is the fastest an less cycles consuming manner to achieve such result?
I was wondering this: is it possible to make an instant XOR of all the buffer content to check if it does return 0 ?the only way is it to cycle through all the bytes and compare each one of them with 0?
I am wonder what is the fastest way of changing elements in array of characters for encode purpose, here is simple example presenting an idea:
Code:
char *a = "123456789":
char b[] = "ABCDEFGHI";
int 1;
for (i=0;i<strlen(a);i++) {
b[i] = a[i];
}
Is this approach better or worse than bit manipulation ?
I have written an SQL statement that would:
1) Count the number of rows in the table booking that are open and where the booking.postcode is "MK",
2) Take a note of the plot (in booking.plot_id), and then update the table plot.jobs with the value count.
For example running the SQL query when booking table has the following rows:
Would see the following highlighted values in plot.jobs being updated to 1:
I managed to resolve it with this code so far (note I am using Connector/Net):
public void RefreshPlot(){
string query =
"SELECT Count(*) AS count, plot_id FROM booking WHERE postcode='MK' AND status='open' GROUP BY plot_id";
var cmd = new MySqlCommand(query, _connection);
var da = new MySqlDataAdapter(cmd);
var dtCounts = new DataTable();
da.Fill(dtCounts);
[code]....
Currently, my code only checks for existing rows in the booking table and updates the plot table. However if the row gets deleted in the booking, then the changes are not reflected in the plot table.
Example: If we delete the row with plot.id=1 and plot.plot_id=4, then booking.plot_id should go back to being 0, if it was initially 1. At the moment, it doesn't. How would I update my SQL statement to better reflect this? In a sense, it should check for "non-existent" rows, i.e. the impact that the row plot.plot_id=4 & plot.id=1 has on booking.plot_id when deleted?
This is my code: [tag]
Code:
#include <iostream>
#include <string>
#include <cstring>
#include <vector>
using namespace std;
[Code] .....
So I'm writing an RPG and I'm in need of an inventory system. Of course as an relatively old member of the forum I know best than just come here and ask so I've already researched quite a bit and I've formulated this idea.
I've kind of conceptualized it like so: I'll have some sort of STL container of a unique_ptr of my base item class. There will be derived item classes. Taking advantage of polymorphism I can then call the new Derivedclass when inserting it in the STL container.
My questions are: What STL container should be used for the inventory(fixed sized)?
What is container class? what its advantage ?
View 2 Replies View RelatedI have a pile of data, which i need to access frequently and fast. One entry consists of two unsigned ints, let`s call them source and destination.
One source can have several destinations, but this rarely ever happens. Several sources can have the same destination - this happens more frequently, but still scarcely.
Once the data is set up, it rarely ever changes - yet it should be possible to add or remove entries.
I now need to find all sources for a given destination, or all destinations for a given source.
The question: which stl container to choose?
I have tried a multimap, using the source as key. This works good for finding all d for a given s, but is inefficient in the other direction.
Do you think it would be more efficient to have two multimaps, sorted respectively by source and destination?
I am trying to come up with a way to make use of a "multilevel dynamic" container. I am parsing a file to grab some pieces of data. Lets say the first field of data I find I push into an array. At the same time lets I wish to create 2 cascaded sublevels. So an element in Modules is a pointer to the Types vector associated with that module and each element in Types is a pointer to a vector of Data. This concept should be similar to memory paging.
/*
Modules Types Data
____ _____ ______
|____|------> |_____| ---------->|______|
|____| |_____| |______|
|____| |_____| |______|
|____|
|____|
|____| _____ ______
|____|------> |_____|----------->|______|
|____| |_____| |______|
*/
Obviously this becomes very hair quickly so it is obvious that I need to dynamically create and destroy vectors (if I do it this way). Should I just create pointers using the new operator?
Here is some of my code if it is even worthwhile to read:
class Parser {
//storage arrays
vector <string> modules;
vector <string> terminal_type;
vector <string> tag_type;
vector <string> data;
[Code] ....
parse this stuff and nicely organize it.
If you take the first one, "max_logvar" is a module so everything between < and > is associated with that module.
symb is unimportant for now.
then "proterm" is a "module type" so then module now needs a module type container but I may have more than one of those.
so then I break it down by "Input" and "Output" where each of those can have the integer values (just in an array where each position will be set) that are in the fields to the right.
I have a container in c++11 and i must delete first object and i don't know how...
for (const prob& p : *static_cast<vector<prob>*>(list.listData)){
// i must delete the first object
}
How do we design a container of objects all of which belong to some subclass which directly/indirectly inherits from a given parent class? Moreover, I would like to have functions that enable me to pick only objects of a certain class type from the container.
For example if the parent class is A and I have a hierarchy of classes that derive from it, we must have a container that can contain any class that exists in this hierarchy. Also, get_B() must be able to let me examine only those objects in this container that inherit (directly/indirectly) from class B (class B exists in the hierarchy rooted at A).
Preferably, we would like to avoid downcasting. Or even explicit typechecking of any sort.
To my understanding, a Container should have an Allocator member data, which is used internally.
Question: what happens, for example, when we swap() two containers that use different allocators?
Must the allocators be swapped as well?
Must all elements of the container be reallocated when the allocator is changed?
I need to create an array container with the same structure as double myA [100][100];. But I cannot declare it as array<double, 100, 100> myA; however I do need this container for its format. How can I make it work.
View 6 Replies View RelatedI know that it's a class that contains data from another class I just do not know how to make them both work together.
View 1 Replies View Relatedi built a programming language called jade that right now can only print. i want to add variables to it however. I am going to use a modified bajarne stroustrop calculator to handle expressions (ie will now include string manipulations and such), but I want to build a var class into the program to make it easier for the program. i want variables to act like python variabes, and arrays to act like python associative arrays. Ive scoured different containers, but they only work if the variable isnt an array in my language, because it will only have one type. the only thing i can come up with is a union and 4 overloaded = operators (for bool, int, double, and string) is there a better way to do this?
View 2 Replies View Relatedso i have a container called Source that is of type std::map<std::string, std::vector<std::string>> but when I try to print it with this function:
void Lexer::PrintSource()
{
for(auto Iterator = this->Source.begin(); Iterator != this->Source.end(); Iterator++)
for(auto SubIterator = Iterator->begin(); SubIterator != Iterator->end(); SubIterator++)
cout<< *SubIterator << endl;
}
i get these errors:
Lexer.cpp: In member function 'void Lexer::PrintSource()':
Lexer.cpp:29:42: error: 'struct std::pair<const std::basic_string<char>, std::vector<std::basic_string<char> > >' has no member named 'begin'
for(auto SubIterator = Iterator->begin(); SubIterator != Iterator->end(); SubIterator++)
^
Lexer.cpp:29:76: error: 'struct std::pair<const std::basic_string<char>, std::vector<std::basic_string<char> > >' has no member named 'end'
for(auto SubIterator = Iterator->begin(); SubIterator != Iterator->end(); SubIterator++)
^
I have a deposit of containers and i must delete the cats container. How i can do that?
#include <iostream>
#include <string>
#include <vector>
using namespace std;
struct Cat {
string name;
int age;
[Code] .....
I want to find all instances of a substring mysub in array container myarr and replace each occurrence of mysub with empty string " ". To do that, I'd like to use for loop with search algorithm.
Code below:
p=array iterator
for ( p=search(myarr.cbegin(),myarr.end(), mysub.begin(),mysub.end();
p!=myarr.end();
p=search(p,myarr.end(),mysub.begin(),mysub.end() ); {
[Code] ......