CODEWITHSUNDEEP
c++
Jacob
Jacob

Reputation: 119

Problem with c++ sorting of objects, vectors

Consider the following code:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

class Vertex {
    public:
    int id;
    vector<Vertex*> edges;
    Vertex(int id) : id(id) {}
    int get_id() const {return id;}
};

class Graph {
    public:
    vector<Vertex*> vertices;
    Graph(int V) {
        vertices.reserve(V);
    }
    void test(vector<Vertex*>& other) {
        sort(vertices.begin(), vertices.end(), [](const Vertex*& one, const Vertex*& two) {return &*one < &*two;});
        sort(other.begin(), other.end(), [](const Vertex*& one, const Vertex*& two) {return &*one < &*two;});
    }
};

When I try to compile the above I get the error: error: no matching function for call to object of type '(lambda at Graph.cpp:59:48)' if (__comp(*--__last, *__first)). I don't understand how I can fix this issue.

Upvotes: 0

Views: 53

Answers (1)

HolyBlackCat
HolyBlackCat

Reputation: 96053

The parameters of your comparators are non-const references. More specifically, "references to non-const pointers to const Vertex".

You either need const references: const Vertex *const &one, or even better, just pass by value: const Vertex *one.

Also note that &*one < &*two is equivalent to one < two.

Upvotes: 3

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