C++ :: How To Iterate Through A For Loop Randomly

Apr 5, 2013

So I have a vector that I want to iterate through randomly, and by random I mean that each element is only accessed once but I don't want to shuffle the vector because the vector elements are large. So I want this functionality:

std::vector<SomeLargeObjectWithoutACopyConstructor> myvec;
// ...fill myvec
std::random_shuffle(myvec.begin(),myvec.end());
for (auto& value : myvec)
{
// do stuff
}

Only I don't want to do this because the object type has no copy constructor and is large, so I don't want to shuffle the vector, just the iteration path. Is there a simple and efficient way of iterating randomly through a vector while ensuring that each object is only accessed once?

View 3 Replies


ADVERTISEMENT

C :: When Try To Iterate Two Times Or More - Program Gets Stuck In Infinite Loop

Mar 18, 2014

I'm having trouble getting my loop to work correctly. If I iterate the for loop once it works as expected and displays proper output. When I try to iterate two times or more the program gets stuck in an infinite loop.

testData8.dat:

Code:
12 9
13 756

View 3 Replies View Related

Visual C++ :: Unable To Iterate Over A Vector In Nested For-Loop

Jan 20, 2014

So I have this problem with not being able to iterate over a vector in a nested for-loop. Here's the nested for-loop:

bool innerHit = false;
for (std::vector<Sprite*>::iterator outerIter = sprites.begin(); outerIter != sprites.end() && (!sprites.empty()); outerIter++) {
Sprite* spriteOne = *outerIter;
for (std::vector<Sprite*>::reverse_iterator innerIter = sprites.rbegin(); innerIter != sprites.rend() && (!sprites.empty()); innerIter++) {
Sprite* spriteTwo = *innerIter;

[Code] .....

What happens is, after having called the collisionDestroy-function and the program tries to execute the nest loop in the outer for-loop, it all crashes with the text "Expression: vector iterator not decrementable", which I understand is because the iterator will have already become useless. The question is: know this, how do I fix it? I can't seem to get a hang of it.

Here's the collisionDestroy-function (the collisionReaction does nothing but sets a few local variables):

void Enemy::collisionDestroy(std::vector<Sprite*>& sprites) {
for (std::vector<Sprite*>::iterator iter = sprites.begin(); iter != sprites.end(); iter++) {
Enemy* tmp = dynamic_cast<Enemy*>(*iter);
if (this == tmp && collisionType == 3 || collisionType == 1) {
sprites.erase(iter);
break;
}
}
}

View 14 Replies View Related

C++ :: Loop Randomly Until Get All Seven Numbers

Nov 13, 2013

Is it possible to loop randomly. For example

for ( int i = 0; i<= 6 ; i++ )

I don't want i to acsend from 0 to 6 but i want it to get all numbers randomly. For example

first time r = 5 second time r = 2 and so on

until it gets all the seven numbers

View 4 Replies View Related

C++ :: Loop Through Indexes In Guess Array And Assign M Randomly

Jan 19, 2013

Just run a loop through each of the indexes in the guessarray and assign 'M' to them randomly.

View 2 Replies View Related

C++ :: For Loop In Hangman Game - Read A Word From Text File Randomly And Matches It With Definition

Jun 26, 2014

Ok here I have a program that reads a word from a text file randomly and matches it with the definition. The user has to guess what the word is according to the definition.

I'm having trouble with my for loop, I'm not getting any errors. But I just know something is off.

Here's my code:

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include <ctime>

using namespace std;
int main(){
int number;
int count = 0;
int numOfGuess = 0;

[Code] ...

This is words.txt:

apple#the usually round, red or yellow, edible fruit of a small tree
boat#a vessel for transport by water
horse#a solid-hoofed plant-eating domesticated mammal with a flowing mane and tail, used for riding
television#a system for transmitting visual images and sound that are reproduced on screens
soup#a liquid dish, typically made by boiling meat, fish, or vegetables, etc.
bottle#a container, typically made of glass or plastic and with a narrow neck
barber#a person who cuts hair
toast#sliced bread browned on both sides by exposure to radiant heat
radar#a system for detecting the presence, direction, distance, and speed of aircraft, ships, and other objects
red#of a color at the end of the spectrum next to orange and opposite violet

View 1 Replies View Related

C :: Merge Two Arrays Without Need To Iterate

Nov 19, 2013

I've come to a point in tuning my algorithm, where I need to sum the elements of two arrays, eg.:

array1: (1,1,1)
array2: (2,2,2)
arrayOut: (3,3,3)

Is there any way how to do that without need to iterate? Some memory hacks?

View 10 Replies View Related

C++ :: How To Use One Index To Iterate Between All The Values

Sep 6, 2013

How can I use one index to iterate between all the values

for example:

//I defined
vector<typeA> VA(XD,typeA());
vector<typeB> VB(XD,typeB());

//then the standard method to iterate is:
for(vector<typeA>::Size_type i=0; i<VA.size(); i++) {
VA[i].functionA();
VB[i].functionB();
}

the other way, use int,

//I defined
vector<typeA> VA(XD,typeA());
vector<typeB> VB(XD,typeB());

//then the standard method to iterate is:
for(int i=0; i<VA.size(); i++) {
VA[i].functionA();
VB[i].functionB();
}

none of above make me feel formal...

View 7 Replies View Related

C++ :: How To Iterate Through A Two Dimensional Vector

Apr 25, 2014

How do I iterate through a two dimensional vector? To iterate through and print the elements of a single dimensional vector I use:

vector<int> a;
for(vector<int>::iterator it=a.begin();it<a.end();it++)
cout<<*it;

How do I do the same for a two dimensional Vector?

View 2 Replies View Related

C++ :: How To Properly Iterate Over A Container

Oct 31, 2013

so 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++)
^

View 6 Replies View Related

C++ :: How To Set Pointer And Iterate Through A Matrix

Aug 8, 2012

How can a set a pointer , to a matrix example matrix[20][20] and iterate ( loop ) in each row first sort of X first and then Y through it using the pointer , how to setup dynamic allocation

through pointer = new matrix[20][20]

and finally call delete on pointer when done with the matrix.

View 4 Replies View Related

C :: Iterate Through A User Inputted Integer?

Oct 5, 2014

I need to allow the user to input an integer of any length and print out the word of each number in the integer. So the user would enter "324562" and then the output would be "three two four five six two". I'm struggling to understand the best way to do it in C. I know I need a loop that goes through the int but I don't know how to do it

View 7 Replies View Related

C++ :: Iterate Through A Vector In Constant Function

Mar 21, 2014

I need to iterate through a vector in a const function, and, as my function is called very often, to get more performances I need my iterator to be declared somewhere else than the function, so it doesn't have to get deleted and recreated over and over again. So here is my code:

class Shop {
public:
//methods
virtual void draw(sf::RenderTarget &target, sf::RenderStates states) const{

[Code] ....

Seems great? Well no. I actually get an error on the "for" line.

It tells me : "You can't use '=' here" and "You can't use the ++ operator here"

The thing is, if I actually declare my iterator in the loop, the compiler stops giving me warnings, but, as I said, I really want to avoid doing that.

View 4 Replies View Related

C++ :: Iterate Through Container And Find Value Mapped To A Specific Key

Jan 14, 2014

A C++ container type called std::map is used to store elements that are formed by a combination of key value and mapped value. How do you iterate through this container and find the value mapped to a specific key?

View 3 Replies View Related

C++ :: Enable Client To Iterate Internal Vector

Nov 26, 2012

The example enable a client to iterate the internal std::vector using being() and end().

Code:
class foo {
public:
typedef std::vector<std::string>const_iterator iter;
iter begin () const;
iter end () const;

[Code] .....

In the future I see the need for this class to be able to control sequence (sorting) and also show a subset of the complete list based on a search parameter.

Using std::sort appear to solve the ability to sort the collection.

How can I return an iterator to the client which only iterates a sub-set of all items in the std::vector?

An example would be, I add this method to the class;

Code:
void find(const std::string& st);

So if the client performs (below) only items in std::vector that contains the character "a" should be possible to iterate.

Code:
foo f;
f.search("a");

One option would be to operate with two collection inside the foo class. One more static containing all items and the other containing the sorted and filtered items. This would lead to some copying but should work. Far from perfect.

View 2 Replies View Related

C++ :: How To Use Dynamic Memory Allocation And Pointers To Iterate Through The Arrays

Dec 21, 2014

I need to use dynamic memory allocation and use pointers to iterate through the arrays that I have already in this program. I am lost, nothing I do works and where to use the pointers. I am just looking for a push in the right direction so I can finish this project and how I can implement pointers in my program.

#include <iostream>
#include <string>
#include <cstdlib>
#include <iomanip>
#include <stdio.h>
using namespace std;

[Code]...

View 1 Replies View Related

C/C++ :: Iterate Through Array And Search For A Number That Was Stored By User

Nov 23, 2014

So I have an issue with a homework assignment that I am coding. I am attempting to get a function to iterate through an array and search for a number that was stored in an array by the user. So far I can take the number, get the numbers displayed but in my menuChoice2 function, for some reason the program is not confirming whether or not the number is entered, and is only telling me that the number has not been found, instead of confirming that the number is in the array.

Here is my code thusfar:

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
// Variables that are Globally declared
int menuChoice = 0;
int usernum[1000] = { ' ' };

[Code] .....

To be clear I am not getting any errors but something is telling me that the error is in the formatting of menuChoice2.

View 14 Replies View Related

C/C++ :: Iterate 2D Matrix In Order To Exchange Columns And Rows Using Pointers

Jan 19, 2014

I am trying to iterate a matrix in order to exchange rows and columns element by element. Although the function that exchanges the rows has come out well, i don't seem to figure out how to do the same on columns.The columns switch for a matrix like

1 2 3
1 2 3
1 2 3

if i try to switch column 3 and 2,is:

1 3 2
1 3 2
1 2 3

Here are both of the functions:

void interchange_rows(int *p,int n,int r1,int r2){
    int temp;
    for(int i=0;i<n;i++){
            temp=*(p+r1*n+i);
            *(p+r1*n+i)=*(p+r2*n+i);
            *(p+r2*n+i)=temp;
   
[Code] ......

View 1 Replies View Related

C++ :: Iterate Through Char Array And Pull IP Addresses To Test If They Respond

Apr 8, 2013

I am trying to write a loop that will iterate through a char array in C and pull the IP addresses and test them to see if they respond. My ultimate goal is to have the first one that responds returned in the function, but the loop is not running correctly. It will run through right the first time, but then will start over again.

Code:
const char * getServer(char *svrList) {
char *srList;
srList = strtok(svrList, " ," );
printf("Contents of srList b4 loop: %s
", srList);
printf("Server List: %s
", svrList);

[Code] ....

Code output:
Contents of srList b4 loop: 1.1.1.1
Server List: 1.1.1.1
result is "1.1.1.1"
Hitting else loop
Contents of srList in else: 2.2.2.2
result is "2.2.2.2"
result is "2.2.2.2"
Contents of srList b4 loop: 1.1.1.1
Server List: 1.1.1.1
result is "1.1.1.1"
Hitting else loop
Contents of srList in else: (null)

View 14 Replies View Related

C :: Max / Min Value In Randomly Produced Array

May 10, 2014

I am very much a beginner at C and a large amount of it still tends to go over my head, I've created a 2d array which its size is generated from user input and filled with random integers. Next I need to locate the maximum and minimum figures in the integer and as dull..This is the code I have so far

Code:

#include <stdio.h>#include <stdlib.h>
int main ()
{
int firstDimension, secondDimension, firstDimensionIndex, secondDimensionIndex,index;
int **table;
}

[code]....

View 2 Replies View Related

C/C++ :: Randomly Moving Characters

Jan 6, 2015

I am making a game and I am attempting to get the zombies to move randomly but for the life of me, I simply don't have the knowledge with srand to do it

#include <iostream>
#include <windows.h>
#include <time.h>

[Code].....

View 13 Replies View Related

C++ :: Getting Sum Of Two Randomly Generated Numbers

Feb 15, 2015

I can't get the sum of two randomly generated numbers - I don't believe the program is adding wrong what I think might be happening is upon hitting enter its adding two new randomly generated numbers -

Code:
// Program functions as a math tutor
#include <cstdlib>
#include <iostream>
#include <ctime>
using namespace std;
int main() {
// Constants
const int Min_Value = 1;

[Code] .....

View 3 Replies View Related

C++ :: Distribute Numbers Randomly - No Duplicates

Dec 13, 2013

I want to create a randomly ordered array of integers where there are no duplicates. Is there a way of doing this in one iteration? Or maybe even a standard function for this?

I'm looking for something like this:
A2 = [3 2 1 6 7 8 4 5]

View 12 Replies View Related

C :: Possible To Set Questions And System Will Randomly Display Each

Aug 5, 2014

I want to create a word game using c. My question is it possible to set questions and the system will randomly display each? If yes, what's the right code?

View 10 Replies View Related

C :: Printing 21 Different Numbers That Are Randomly Generated?

Mar 2, 2014

The program is supposed to be printing 21 different numbers that are randomly generated. Why am I getting the same number 21 times? Using dev C++ compiler.

Code:

/*prints random numbers between 1 - 99*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

[Code]......

View 3 Replies View Related

C++ :: Generate Randomly 3 Objects Of Types

Nov 17, 2014

Is there any way to generate random types I build? I know rand command returns random integers, but I want to create some classes and and a function that will generate randomly 3 objects of the types I have created.

View 1 Replies View Related







Copyrights 2005-15 www.BigResource.com, All rights reserved