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vector/array advice please

csx
Hi all,
I have the following code, which at the moment is a vector of arrays. But
unfortunately, it doesnt do what I want.
Basically, here is an example in Java that I want to work in C++.

var Levels = new Array()

Levels[0] = new makearray(1,1,'b',1);
Levels[1] = new makearray(2,2,'g',1);
Levels[2] = new makearray(3,5,'h',1);
Levels[3] = new makearray(4,5,'w',1);
Levels[4] = new makearray(5,3,'p',1);

Can use levels.length() // to return the size of the outer array - i.e. 5

This is really easy in Java, its like an array of arrays but with the
levels.length() feature of a vector, and I want the same in C++. Also, you
dont have to specify the size of the array beforehand.

I want to be able to specify an array by its corresponding array index. So,
if i wanted array (4, 5, 'w', 1) this would be accessed like
nodes temp = Levels[3].
But I also want to be easily able to call levels.length() so that I can get
the size of the array. In this case, 5.

I implemented mine as a vector of arrays, so that I could use
"nodes.size()", but now I cant refer to them via index. i.e. node[4].
If I had implemented it as an array of arrays, the index would work,
node[4]. but I wouldn't be able to call a method like nodes.size().

Can someone please provide some advice
Thanks in advance!!




#include "stdafx.h"
#include <vector>
#include <iostream> // we have to use STD::cout with this
#include <string>
using namespace std; // Now don't need to specify the namespace, i.e.
STD::COUT

struct node
{
int key, row, parent;
char description;
node( int k=0, int r=0, char d='temp', int p=0 )
: key(k), row(r), description(d), parent(p) {}
};

int _tmain(int argc, _TCHAR* argv[])
{
vector<node> nodes;
nodes.push_back( node(1,4,'G',4) ); // 0
nodes.push_back( node(2,2,'H',2) ); // 1
nodes.push_back( node(3,6,'J',2) ); // 2
return 0;
}


Jul 19 '05 #1
4 2464
csx escribió:
I implemented mine as a vector of arrays, so that I could use
"nodes.size()", but now I cant refer to them via index. i.e. node[4].
If I had implemented it as an array of arrays, the index would work,
node[4]. but I wouldn't be able to call a method like nodes.size().


Use a vector of vectors.

Regards.
Jul 19 '05 #2

"csx" <cs*@ms.com> wrote in message news:bk**********@hercules.btinternet.com...
Levels[0] = new makearray(1,1,'b',1) Pretend we're not javaheads here and explain what makearray does.
I implemented mine as a vector of arrays, so that I could use
"nodes.size()", but now I cant refer to them via index. i.e. node[4].
If I had implemented it as an array of arrays, the index would work,
node[4]. but I wouldn't be able to call a method like nodes.size().


Can't refer to what by index. Sure you can refer to nodes[4] (it will
even work if there were that many items in the array). The only thing
that won't work is accessing them by index if they do not exist
(perhaps java arrays auto extend, but C++ vectors do not).

vector<node> nodes;
node[0] = node(2,3,'d',3); // illegal, nodes has zero size.

nodes.push_back( node(1,4,'G',4) ); // 0
node[0] = node(5,6,'7',8); // legal the push_back increased nodes.size() to 1.

nodes.resize(5);
node[2] = node(7,8,'9',10); // legal, resize increased the size.
Jul 19 '05 #3
csx
hi thanks
but, how would this be coded so i could index a vector via
vector[4] as in the code posted earlier?

"Julián Albo" <JU********@terra.es> wrote in message
news:3F***************@terra.es...
csx escribió:
I implemented mine as a vector of arrays, so that I could use
"nodes.size()", but now I cant refer to them via index. i.e. node[4].
If I had implemented it as an array of arrays, the index would work,
node[4]. but I wouldn't be able to call a method like nodes.size().


Use a vector of vectors.

Regards.
Jul 19 '05 #4
"csx" <cs*@ms.com> wrote in message
news:bk**********@hercules.btinternet.com...
hi thanks
but, how would this be coded so i could index a vector via
vector[4] as in the code posted earlier?


First resist top-posting.

Second, you usually construct a vector using push_back.

std::vector<std::string> v;
v.push_back( "a " );
v.push_back( "example " );
v.push_back( "simple " );

and then you use the data using operator[].

example:
std::cout << v[0] << v[2] << v[1] << std::endl;
// prints "a simple example "

Alternatively, use std::map.

std::map<int, std::string> v;
v[0] = "a ";
v[0] = "a ";

Jul 19 '05 #5

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