Quick vector copy

This is a discussion on Quick vector copy within the C++ Programming forums, part of the General Programming Boards category; Hi, what is the quickest (most processor efficient) way of copying from one vector to another? thanks....

  1. #1
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    Quick vector copy

    Hi, what is the quickest (most processor efficient) way of copying from one vector to another?

    thanks.

  2. #2
    Moderately Rabid Decrypt's Avatar
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    Do you want to copy the entire vector, or just a part of it?
    There is a difference between tedious and difficult.

  3. #3
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    The entire vector is all I need.

    I'm currently copying it all using a loop and pushing each item from the source vector to the target vector one at a time - but I'm trying to optimize my code.

    thanks,

  4. #4
    Tropical Coder Darryl's Avatar
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    Code:
    #include<vector>
    #include<iostream>
    using namespace std;
    
    int main()
    {
    	vector<int> v1;
    	v1.push_back(10);
    	v1.push_back(5);
    	v1.push_back(9);
    	// You can initialize a vector from another
    	vector<int>v2(v1);
    	// You can assign a vector to another
    	vector<int> v3;
    	v3 = v2;
    	
    	cout << v3[0] << ", " << v3[1] << ", " << v3[2] << endl;
            // outputs: 10, 5, 9
    }
    Last edited by Darryl; 12-06-2005 at 08:47 AM.

  5. #5
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    If you won't need your source vector after the copy, the quickest way is to use swap because it doesn't actually copy anything.
    Code:
    v1.swap(v2);
    Otherwise, initialization or assignment as Darryl showed is the best way (assuming both vectors hold the same type).

  6. #6
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    that's great - thanks

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