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?
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.
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.
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;
}
}
}
Suppose I have a two-dimensional stl vector (a vector of vectors), for example:
Code : vector<vector<int> > x;
And then I want to sort the outer vectors in order of the size of their inner vectors. How do I do this?
Usually, with a one-dimensional vector, I can just create a comparison function and use the sort function. For example, if my vector is defined as:
Code:
vector<int> y;
And I want to sort if in terms of the int values of each vector element, then I can sort by using the stl::sort function, with the comparison function defined as:
Code:
static bool SortFunction(int val1, int val2) {
if (val1 > val2) {
return true;
} else {
return false;
}
};
However, with my two-dimensional vector, I use the following comparison function:
Code:
static bool SortFunction(vector<int> vec1, vector<int> vec2) {
if (vector1.size() > vector2.size()) {
return true;
} else {
return false;
}
};
I get a runtime error:
"Debug Assertion Failed!
File: c:Program Files (x86)Microsoft Visual Studio 10.0VCincludealgorithm
Line 3686
Expression: invalid operator<"
Why is this?
I have to create a class to represent a 2 dimensional vector. I need to include certain member functions such as a function to find magnitude of the vector, and one to find the dot product of that vector with another vector, and several others too. That's all fine. A stipulation of the problem is that I must include a constructor which can take cartesian form of the vector and a constructor which can take polar form of vector. Since this involves overloading the constructor the best solution I have come up with is to create the object with either doubles or floats so that the compiler can choose the correct constructor. This seems like a really bad idea. Is there a way I can get the compiler to choose the correct constructor without doing it using the precision? Here is a sample of my header file, there are many more member functions
class Vector{
public:
Vector(double x, double y, double v, double w){
myArray[0]=x;
myArray[1]=y;
additionalArray[0]=v;
additionalArray[1]=w;
[Code] .....
In my .cpp file the object is created with either four doubles or four floats depending on which constructor I want to implement. There must be a better way. Additional Array is created for use in member function which require calculations with a second 2d vector.
#include <iostream>
#include <cassert>
#include <vector>
using namespace std;
vector<int> flatten(int a[100][200]) {
vector<int> v;
for (int i = 0; i < 100; ++i) {
[Code]...
I made a function for two dimensional arrays with vector, but I don't know how to make the test code for it.
I am using 2 ARRAYS OF DIFFERENT SIZES in One 2-Dimensional Vector, and my output is not correct. The arrays are size 4 and size 13.
I want COLUMN 0 to have: 55, 66, 77, 88.
I want COLUMNs 1-12 to have 1,2,3,4,5,6,7,8,9,10,10,10,11 in EACH ROW. It would seem that the 2nd loop for the size 13 array would need to loop 4 times in order to fill 4 rows, however, I'm not sure how to do that. Here is what I have so far in code and output:
#include <iostream>
#include <vector>
using namespace std;
int main() {
int typeArray[4] = {55,66,77,88};
int valArray[13] = {1,2,3,4,5,6,7,8,9,10,10,10,11};
[Code] ....
OUTPUT:
55 0 0 0 0 0 0 0 0 0 0 0 0
1 2 3 4 5 6 7 8 9 10 10 10 11
77 0 0 0 0 0 0 0 0 0 0 0 0
88 0 0 0 0 0 0 0 0 0 0 0 0
How to populate rows correctly?
Two Hard-coded Arrays into One 2-Dimensional Vector I have 2 arrays, each of them are hard-coded with integer values. I also have one 2-Dimensional vector and I want to put 1 array into the first column of the vector and the other array into the 2nd column of the vector. The reason is that I want to do math on the 2nd column of the vector only.
I am able to accomplish this with 3 arrays. Two of them are 1-Dimensional and the third array is 2-Dimensional.
I know how to pass ONE Array into ONE vector:
Code:
vector<int> myVector(typeArray, typeArray + 4);
however, when I declare a 2-Dimensional vector:
Code:
vector< vector <int> > myVector(3, vector<int> (2,0))
I am not seeing how to add TWO arrays or how to OUTPUT it to the screen.
Here is my code using DevCPP:
#include <iostream>
#include <vector>
#include <Windows.h>
[Code]...
I don't get any errors, however, I don't know how to output it to the screen to see what it looks like.
How can I concatenate two 2-dimensional int arrays into one larger 3-dimensional array. This question is also valid for the 3-dimensional vectors. I know the command for the one dimensional vector as:
std::vector<int> results;
results.reserve(arr1.size() + arr2.size());
results.insert(results.end(), arr1.begin(), arr1.end());
results.insert(results.end(), arr2.begin(), arr2.end());
and for the one dimensional array as:
int * result = new int[size1 + size2];
copy(arr1, arr1 + size1, result);
copy(arr2, arr2 + size2, result + size1);
But I do not know how to make a 3-dimensional array or vector.
I had a hard question in my C++ final exam and I'm trying to solve it for the last 3 days. I haven't succeded yet! Here is the question: You have a one-dimensional array A[20]={1,2,3,4,...,20} and B[5][4] you have to assign the A array's elements to the B array but there is an order which is: B[5][4] = { { 12, 9, 11, 10 }, { 14, 7, 13, 8 }, { 16, 5, 15, 6 }, { 18, 3, 17, 4 }, { 20, 1, 19, 2 } } and there is a restriction: you can only use ONE for statement, nothing else!
#include <iostream>
#include <iomanip>
using namespace std;
int main(){
int A[20] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20 }; // define A array's elements.
int B[5][4] = { 0 }, k = 1; // define B array and k counter.
[code]....
I can't narrow the statements to one,This program works perfectly but it shouldn't be that long, we need ONLY ONE FOR statement, not two!
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?
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?
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...
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++)
^
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.
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 RelatedA 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 RelatedI'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
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]...
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.
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] ......
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)
is it allowed to to like this:
char a[10] = "Lizard";
char b[2][5];
b[0][0] = a[0];
b[0][1] = a[1]; etc?
I have a 3D array that contains 200 strings. I'm trying to copy all these strings into a 2D array. How can this be done? This is what I have so far but it isn't working correctly.
Code:
for(int i = 0; i < row; i++) {
for (int j = 0; j < col; j++)
{
dest[i][j] = source[0][i][j];
} }
The finished product would be with 100 rows, 2 columns.
convert an one dimensional array into a two dimensional array and print like a matrix.
input: 34 50 2 4 90 33 7 80 9
output: A is a 3x3 matrix
34 50 2
4 90 33
7 80 9