How can I replace specific values in a vector in C ++?
I have a vector with some values (3, 3, 6, 4, 9, 6, 1, 4, 6, 6, 7, 3) and I want to replace every 3 with 54 or every 6 1, for example, etc. .d.
So I need to go through the vector first, get the value of [i], find and replace every 3 with 54, but still keep the corresponding positions.std::set
vector::swap
good way? I'm not even sure how to start this :( I can't use push_back
it as it won't preserve the correct order of the values as it's important.
Please keep it simple; I'm just a beginner :)
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Tool for the job std::replace
:
std::vector<int> vec { 3, 3, 6, /* ... */ };
std::replace(vec.begin(), vec.end(), 3, 54); // replaces in-place
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You can use replace or replace_if .
#include<vector>
#include<algorithm>
#include<iostream>
#include<iterator>
using namespace std;
class ReplaceFunc
{
int mNumComp;
public:
ReplaceFunc(int i):mNumComp(i){}
bool operator()(int i)
{
if(i==mNumComp)
return true;
else
return false;
}
};
int main()
{
int arr[] = {3, 3, 6, 4, 9, 6, 1, 4, 6, 6, 7, 3};
std::vector<int> vec(arr,arr + sizeof(arr)/sizeof(arr[0]));
cout << "Before\n";
copy(vec.begin(), vec.end(), ostream_iterator<int>(cout, "\n"));
std::replace_if(vec.begin(), vec.end(), ReplaceFunc(3), 54);
cout << "After\n";
copy(vec.begin(), vec.end(), ostream_iterator<int>(cout, "\n"));
return 0;
}
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Use STL algorithm for_each
. This is not required for the loop and you can do it in one shot using the function object as shown below.
http://en.cppreference.com/w/cpp/algorithm/for_each
Example:
#include <iostream>
#include <algorithm>
#include <vector>
#include <iterator>
using namespace std;
void myfunction(int & i)
{
if (i==3)
i=54;
if (i==6)
i=1;
}
int main()
{
vector<int> v;
v.push_back(3);
v.push_back(3);
v.push_back(33);
v.push_back(6);
v.push_back(6);
v.push_back(66);
v.push_back(77);
ostream_iterator<int> printit(cout, " ");
cout << "Before replacing" << endl;
copy(v.begin(), v.end(), printit);
for_each(v.begin(), v.end(), myfunction)
;
cout << endl;
cout << "After replacing" << endl;
copy(v.begin(), v.end(), printit);
cout << endl;
}
Output:
Before replacing
3 3 33 6 6 66 77
After replacing
54 54 33 1 1 66 77
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