CODEWITHSUNDEEP
c++sorting
Fall0ut
Fall0ut

Reputation: 71

Invalid Operands to Binary Expression Person and Person

I know this question has been asked before in similar circumstances, however I am new to C++ and cannot figure out what needs to be done or why it has to be done. Basically I am using a Person object that I created which has the variables name, age, height, and weight. I need to run a Quick Sort on the Person objects that I have created and sort them by age.

Person Class:

class Person{
private:
    string name;
    int age, height, weight;
public:
Person(string name = "empty", int age = 0, int height = 0, int weight = 0)
{
    this->name = name;
    this->age = age;
    this->height = height;
    this->weight = weight;
};

Quick Sort Method: 

// Quick Sort
void QuickSort(Person *A, int start, int end){
    if(start < end){
        int p = partition(A, start, end);
        QuickSort(A, start, p - 1);
        QuickSort(A, p + 1, end);
    }
}
int partition(Person *A, int start, int end){
    Person pivot = A[end];
    int p = start;
    for(int i = start; i <= end - 1; i++){
        if(A[i] <= pivot){
            Person temp = A[i]; A[i] = A[p]; A[p] = temp;
            p++;
        }
    }
    Person temp = A[end]; A[end] = A[p]; A[p] = temp;
    return p;
}

I am getting the error "Invalid operands to binary expression ('Person' and 'Person) on the line:

if(A[i] <= pivot)

Any help would be appreciated because I have tried multiple things and I have looked it up but cannot get other suggestions to work in this situation. I would appreciate an explanation as to why I was getting this error too if possible. Thanks!

Upvotes: 2

Views: 297

Answers (2)

Barmar
Barmar

Reputation: 781096

You said you want to sort by age, so you need to compare their ages:

if (A[i].age <= pivot.age)

Your code gets an error because you haven't defined a <= operator for your Person class.

Upvotes: 3

Ian Neal
Ian Neal

Reputation: 113

C++ doesn't automatically know how to perform a comparison on class Person.

If you just want to sort by age, try

if(A[i].age <= pivot.age)

If you want to learn about defining special operators so that "Person <= Person" will work automatically, check out cppreference.com: http://en.cppreference.com/w/cpp/language/operators

Upvotes: 5

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