how to change the element of vector

how can i change the element of vector.
for example the vector is : 3,2,5,8,7
i want to change the second number 2 to 6

Code:

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std::vector<int> arr;
arr.push_back(3);
arr.push_back(2);
arr.push_back(5);
arr.push_back(8);
arr.push_back(7);

// method 1
arr[1] = 6;

// method 2
std::vector<int>::iterator pos = arr.begin() + 1;
*pos = 6;

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See this article on std::vector.

Instead of accessing elements by its index you´d better use the replace function (in case you want to replace all occurences...):

Code:

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std::vector<int> arr;
arr.push_back(3);
arr.push_back(2);
arr.push_back(5);
arr.push_back(8);
arr.push_back(7);

// replace all occurences
replace( arr.begin(), arr.end(), 2,6 );

// replace first occurence of 2
std::vector<int> pos = find( arr.begin(), arr.end(), 2 );
if( pos != arr.end() )
{
  *pos = 6;
}

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Regards,
Guido

Quote:

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Instead of accessing elements by its index you´d better use the replace function (in case you want to replace all occurences...):

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Don't you think that depends on the logic of the program? What if he wants to change the third occurence of 2 with 6? In that case none of your samples (which are good OTOH) can help.

Quote:

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Originally Posted by cilu

Don't you think that depends on the logic of the program? What if he wants to change the third occurence of 2 with 6? In that case none of your samples (which are good OTOH) can help.

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I agree with that... but somehow you have to know which element you want to replace. I wanted to show how you can replace items regardless of their position.
However, if you want to replace an item that requires certain criterions you can use replace_if and provide a predicate that checks these criterions.

Regards,
Guido

thanks

but i can`t find the problem with my code

Code:

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void CDelta::Decompose( int m, int n)
{
 int index = 0;
 if( m==0 )
  CreateU( index++ );
 else
  for( int i = m; i >= 1; i-- )
  {
  if( n == 0 || i <= m_vectTemp[n-1] )
  {
        if( m_vectTemp.size() > n )
        m_vectTemp[n] = i;
        else
        m_vectTemp.push_back( i );
        Decompose( m-i, n+1 );
  }
  }
/* 
        int i;
 if(m==0)
  show(n);
 else
  for(i=m;i>=1;i--)
  if(n==0||i<=a[n-1])
  {
        a[n]=i;
        decompose(m-i,n+1);
  }
*/
}

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there is no error when debugging, but it prompt error when running

What is the error that it prompts?

the system show a dialog which prompt:
there is something wrong with vector.exe, it must be colsed...........
please send the report of problem to Microsoft............
( i just translated it to english )

Does the vector contain some elements when you call Decompose? Can you post the code where it calls Decompose the first time?

i just inited it as vector< int > m_vectTempbut when i push some zeros in it,
the system prompted error also

the error was prompted when the first time to run to m_vectTemp[n] = i
(n == 0 )

well if n==0 then the second condition in your if statement would be m_vectTemp[0-1] which clearly is an error.

if( n == 0 || i <= m_vectTemp[n-1] )
if n==0 the second condition will not be judged

IMHO the second condition is still judged.

Oh my god!
the error happend not in the function of Decompose but CrateU
:cry:

Quote:

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Originally Posted by Sarevok

IMHO the second condition is still judged.

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Ok I was wrong. I tried it and the second condition was not judged. My bad.:o

Quote:

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Originally Posted by blacksource

Oh my god!
the error happend not in the function of Decompose but CrateU
:cry:

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:eek: ok you should have just used the debug tools in the first place.