How to find indexes from vector1 in vector2 in c++ - c++

Question

i was envolving about a week with this issue, i have two vector for example vec1 and vec2, i want after search and find values from vec1 in vec2 return their indexes where only found for example:
vector<int>vec2 = { 1, 2, 2, 4 };
vector<int>vec1 = { 1, 2, 4 };
i want somthing like this pseudo code and this result:
pseudo code:
for i = 0 to vec2.size() do
return vec1 indexes in vec2;
end
result:
pass1:
1 0 0 0
pass2:
0 1 1 0
pass3:
0 0 0 1
final resault:
0 0 0 1
My code (it does not compile):
My code:
#include <vector>
#include <iostream>
using namespace std;
vector<int> find_index(vector<int>vec2, vector<int>vec1)
{
std::vector<double> tmp;
for (int i = 0; i<vec2.size(); i++)
{
for (int j = 0; j<vec2.size(); j++)
{
if (vec2[i] == vec1[j])
{
tmp.push_back(i);
}
}
}
return tmp;
}
int main()
{
vector<int>vec2 = { 1, 2, 2, 4 };
vector<int>vec1 = { 1, 2, 4 };
cout << find_index(vec2, vec1);
getchar();
return 0;
}

Answer 1

The code you have fails to compile for two reasons:
Using double item type for the tmp vector. A vector<double> does not convert implicitly to the required function result type vector<int>.
The standard library does not define output of vectors, so the cout << a vector in main doesn't compile.
To output the vector you can define function like this:
void write_to( ostream& stream, vector<int> const& v )
{
for( int i = 0; i < int( v.size() ); ++i )
{
stream << (i > 0? " " : "") << v[i];
}
}
and call it like this:
write_to( cout, find_index(vec2, vec1) );
cout << "\n";
It's also possible to write a little glue code that would enable the cout << notation, i.e. that would make it use the write_to function, but that is maybe just complication now.
With these changes your code compiles and outputs
0 1 2 3