vector push_back array

This is a discussion on vector push_back array within the C++ Programming forums, part of the General Programming Boards category; hi, I've recently changed some code in my program from a multidimensional array to a vector, and I'm wondering if/how ...

  1. #1
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    vector push_back array

    hi,

    I've recently changed some code in my program from a multidimensional array to a vector, and I'm wondering if/how it's possible to initialise a vector array.
    i.e.
    vector<int> MyVector;
    MyVector.push_back(int1,int2,int3,int4,int5);

    old code:
    Code:
    	//header
    	extern int LIST[][5];
    
    	//source
    	int LIST[][5] = 
    	{
    		{24,3,2,5,16};
    		{24,2,5,16,3};
    		{n1,n2,n3,n4,n5};
    	};

    //new code
    Code:
    	//header
    	extern vector<int> LIST[5];
    
    	//source
    	void Create_List()
    	{
    		FillList(24,3,2,5,16);
    		FillList(24,2,5,16,3);
    		FillList(n1,n2,n3,n4,n5);
    	}
    
    	bool FillList(int i1, int i2, int i3, int i4, int i5)
    	{
        		LIST[0].push_back(i1);
        		LIST[1].push_back(i2);
        		LIST[2].push_back(i3);
        		LIST[3].push_back(i4);
        		LIST[4].push_back(i5);
    
    		return true;
    	}


    At the moment, I use FillList() function to populate the vector. Just wondering if there's a better way to do this other than calling another function each time ?


    Thanks!

  2. #2
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    If you also have the array, you can pass that to the vector constructor so that the vector gets initialized with the values in the array.
    Code:
    vector<int> list(list_array, list_array + sizeof(list_array) / sizeof(int));

  3. #3
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    Thanks for the reply!
    Was a little stuck but managed to figure it out from your post.

    Code:
        vector<int> iVec(*iListArray,*iListArray+sizeof(iListArray) / sizeof(int));

    How would one access then a particular element within vector, like you do an array given the above initialisation?
    i.e.
    Code:
    int LIST[][5] = 
    {
        {1,2,3,4,5},
        {6,7,8,9,10},
    };
    
    cout << LIST[2][3];
    cout << iVec[i][j] doesn't work with the above particular setup?


    Thanks!

  4. #4
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    Firstly, iVec would need to be either an array of vectors, or a vector of vectors (otherwise the two-dimensional syntax is invalid).

    Each element of iVec would then be a vector (which can each be initialised using an approach like that described by MemLoop). You won't be able to avoid either some loop construct and/or usage of some temporary array (or vector) of ints.

    When you start going to multiple dimensions with vectors, things become (literally) recursive.
    Right 98% of the time, and don't care about the other 3%.

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