CPP

custom comparator in set of struct

#include <bits/stdc++.h>
using namespace std;

struct Edge {
	int a,b,w;
};

bool cmp(const Edge& x, const Edge& y) { return x.w < y.w; }

int main() {
	//... preciding code
    // declaring set of edge using comparator as a function
	set<Edge,bool(*)(const Edge&,const Edge&)> v(cmp);
    // another way of declaring set fof edge using comparator as a function
	set<Edge,decltype(&cmp)> v(cmp);    
	for (int i = 0; i < M; ++i) {
		int a,b,w; cin >> a >> b >> w;
		v.insert({a,b,w});
	}
	// ... succeeding code
}





// another way using lambda function
auto cmp = [](const Edge& x, const Edge& y) { return x.w < y.w; };

int main() {
	// ... preceding code
	set<Edge,bool(*)(const Edge&,const Edge&)> v(cmp);
	for (int i = 0; i < M; ++i) {
		int a,b,w; cin >> a >> b >> w;
		v.insert({a,b,w});
	}
	// ... succeeding code
}
// You can also use the following syntax to declare set v using a lambda

set<Edge,decltype(cmp)> v(cmp);