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Finding Vector(includes objects) Element's Index by Element

bydrachen (57)
I'm trying to find the index of a vector element. Vector includes class objects. But I can't find a way.

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#include <vector>
#include <algorithm>
#include <iostream>

class myClass
{
    int a;
};

void indexfinder (std::vector<myClass>& vec1, myClass& _key)
{
    auto i = std::find(vec1.begin(), vec1.end(), _key);

    //if it's found
    if (i != vec1.end())
    {
        int k = i - vec1.begin();
        std::cout << k;
    }

    //if it's not found
    else
        std::cout << -1;
}

int main()
{
    myClass abc1;
    myClass abc2;
    myClass abc3;
    std::vector<myClass>vec1 {abc1, abc2, abc3};
    indexfinder(vec1,abc3);
}


I tried this without class, just with integers and it was working. This code is giving a lot of errors with class objects. Especially says there's no operator== for this type or smth.
bydrachen (57)
I found a solution like this and it's working with this example

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#include <vector>
#include <iostream>

class myClass
{
public:
    int a;

    bool operator== (myClass _x)
    {
        if (this->a == _x.a)
            return 1;
        else
            return 0;
    }
};

void indexfinder (std::vector<myClass>& vec1, myClass& _key)
{
    for (auto i = 0; i <(int) vec1.size(); i++)
    {
        if (vec1.at(i) == _key)
            std::cout << i;
    }
}

int main()
{
    myClass abc1;
    abc1.a = 0;

    myClass abc2;
    abc2.a = 0;

    myClass abc3;
    abc3.a = 5;

    std::vector<myClass>vec1 {abc1, abc2, abc3};
    indexfinder(vec1,abc3);
}
seeplus (6589)
Perhaps this:

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#include <vector>
#include <algorithm>
#include <iostream>

class myClass
{
	int a {};
public:
	myClass(int a_) : a(a_) {}

	friend bool operator==(const myClass& a, const myClass& b) {
		return a.a == b.a;
	}
};

void indexfinder(const std::vector<myClass>& vec1, const myClass& _key) {
	const auto i { std::find(vec1.begin(), vec1.end(), _key) };

	//if it's found
	if (i != vec1.end()) {
		const auto k { std::distance(vec1.begin(), i) };

		std::cout << k;
	}
	//if it's not found
	else
		std::cout << -1;
}

int main() {
	myClass abc1(1);
	myClass abc2(2);
	myClass abc3(3);

	std::vector<myClass>vec1 { abc1, abc2, abc3 };
	indexfinder(vec1, abc3);
}

Last edited on
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