Graph implementation using STL for competitive programming | Set 2 (Weighted graph)

In Set 1, unweighted graph is discussed. In this post, weighted graph representation using STL is discussed. The implementation is for adjacency list representation of weighted graph.

graph-stl

We use two STL containers to represent graph:

  • vector : A sequence container. Here we use it to store adjacency lists of all vertices. We use vertex number as index in this vector.
  • pair : A simple container to store pair of elements. Here we use it to store adjacent vertex number and weight of edge connecting to the adjacent.

The idea is to use a vector of pair vectors. Below code implements the same.

// C++ program to represent undirected and weighted graph
// using STL. The program basically prints adjacency list
// representation of graph
#include <bits/stdc++.h>
using namespace std;

// To add an edge
void addEdge(vector <pair<int, int> > adj[], int u,
                                     int v, int wt)
{
    adj[u].push_back(make_pair(v, wt));
    adj[v].push_back(make_pair(u, wt));
}

// Print adjacency list representaion ot graph
void printGraph(vector<pair<int,int> > adj[], int V)
{
    int v, w;
    for (int u = 0; u < V; u++)
    {
        cout << "Node " << u << " makes an edge with \n";
        for (auto it = adj[u].begin(); it!=adj[u].end(); it++)
        {
            v = it->first;
            w = it->second;
            cout << "\tNode " << v << " with edge weight ="
                 << w << "\n";
        }
        cout << "\n";
    }
}

// Driver code
int main()
{
    int V = 5;
    vector<pair<int, ints> > adj[V];
    addEdge(adj, 0, 1, 10);
    addEdge(adj, 0, 4, 20);
    addEdge(adj, 1, 2, 30);
    addEdge(adj, 1, 3, 40);
    addEdge(adj, 1, 4, 50);
    addEdge(adj, 2, 3, 60);
    addEdge(adj, 3, 4, 70);
    printGraph(adj, V);
    return 0;
}

Output:

Node 0 makes an edge with 
	Node 1 with edge weight =10
	Node 4 with edge weight =20

Node 1 makes an edge with 
	Node 0 with edge weight =10
	Node 2 with edge weight =30
	Node 3 with edge weight =40
	Node 4 with edge weight =50

Node 2 makes an edge with 
	Node 1 with edge weight =30
	Node 3 with edge weight =60

Node 3 makes an edge with 
	Node 1 with edge weight =40
	Node 2 with edge weight =60
	Node 4 with edge weight =70

Node 4 makes an edge with 
	Node 0 with edge weight =20
	Node 1 with edge weight =50
	Node 3 with edge weight =70

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