sorting the edges in nondecreasing order of weight. For example, the sample contains the following edges:

1 2 9 1 3 7 2 3 10 2 4 3 After sorting, it should look like

2 4 3 1 3 7 1 2 9 2 3 10 With C++, the easiest method is to use a vector of nested pairs:

sort(v.begin(), v.end(), [](auto & it1, auto & it2) {
		return it1.first < it2.first;
	});

This above is a lambda expression

#include <iostream>
#include <bits/stdc++.h>
#include <algorithm>
#include <vector>
using namespace std;
int main() {
	int M = 4;
	vector < pair<int, pair<int, int>>>v; //given as {wi,{xi,yi}}
	while (M--) {
		int a, b, w;
		cin >> a >> b >> w;
		v.push_back({w, {a, b}});
	}
	cout << "before sorting: \n";
	for (auto it : v) {
		cout << it.first << " " << it.second.first << " " << it.second.second << "\n ";
	}
	sort(v.begin(), v.end(), [](auto & it1, auto & it2) {
		return it1.first < it2.first;
	});
	cout << "\nafter Sorting\n";
	for (auto it : v) {
		cout << it.first << " " << it.second.first << " " << it.second.second << "\n ";
	}
	return 0;
}

Classes

First, we need to define a class that represents what we want to sort. In our example we will define a class Edge that contains the two endpoints of the edge and the weight.

C++

A C++ struct is the same as a class in C++, but all members are public by default.

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

struct Edge {
	int x, y, w;
};

//Alternatively, We can use

// class Edge {
// public:
// 	int x, y, w;
// };
int main() {


	int M = 4;
	vector <Edge>v; //given as {wi,{xi,yi}} we got rid of pair<int, pair<int, int>> See.
	while (M--) {
		int a, b, w;
		cin >> a >> b >> w;


		v.push_back({a, b, w});

	}
	cout << "before sorting: \n";
	for (auto it : v) {
		cout << it.x << " " << it.y << " " << it.w << "\n ";
	}

	sort(v.begin(), v.end(), [](auto & it1, auto & it2) {
		return it1.w < it2.w;
	});

	cout << "\nafter Sorting\n";

	for (auto it : v) {
		cout << it.x << " " << it.y << " " << it.w << "\n ";
	}
     return 0;
}