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Graph implementation using STL for competitive programming | Set 2 (Weighted graph)
  • Difficulty Level : Easy
  • Last Updated : 10 May, 2021

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++




// 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, int> > 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;
}

Python3




# Python3 program to represent undirected
# and weighted graph. The program basically
# prints adjacency list representation of graph
 
# To add an edge
def addEdge(adj, u, v, wt):
     
    adj[u].append([v, wt])
    adj[v].append([u, wt])
    return adj
 
# Print adjacency list representaion ot graph
def printGraph(adj, V):
     
    v, w = 0, 0
    for u in range(V):
        print("Node", u, "makes an edge with")
 
        for it in adj[u]:
            v = it[0]
            w = it[1]
            print("\tNode", v, "with edge weight =", w)
             
        print()
 
# Driver code
if __name__ == '__main__':
     
    V = 5
    adj = [[] for i in range(V)]
 
    adj = addEdge(adj, 0, 1, 10)
    adj = addEdge(adj, 0, 4, 20)
    adj = addEdge(adj, 1, 2, 30)
    adj = addEdge(adj, 1, 3, 40)
    adj = addEdge(adj, 1, 4, 50)
    adj = addEdge(adj, 2, 3, 60)
    adj = addEdge(adj, 3, 4, 70)
 
    printGraph(adj, V)
 
# This code is contributed by mohit kumar 29

Javascript




<script>
// Javascript program to represent undirected and weighted graph
// using STL. The program basically prints adjacency list
// representation of graph
 
    // To add an edge
    function addEdge(adj,u,v,wt)
    {
        adj[u].push([v,wt]);
        adj[v].push([u,wt]);
        return adj;
       
    }
     
    //Print adjacency list representaion ot graph
    function printGraph(adj, V)
    {
        let v=0,w=0;
        for(let u=0;u<V;u++)
        {
            document.write("Node "+u+ " makes an edge with<br>");
            for(let it=0;it<adj[u].length;it++)
            {
                v=adj[u][it][0];
                w=adj[u][it][1];
                document.write("        Node "+ v+ " with edge weight ="+ w+"<br>")
            }
        }
    }
     
     
    // Driver code
    let V = 5;
     
    // The below line may not work on all
    // compilers.  If it does not work on
    // your compiler, please replace it with
    // following
    // vector<int> *adj = new vector<int>[V];
    let adj=new Array(V);
    for(let i=0;i<V;i++)
    {
        adj[i]=[];
    }
     
    // Vertex numbers should be from 0 to 4.
    adj = addEdge(adj, 0, 1, 10)
    adj = addEdge(adj, 0, 4, 20)
    adj = addEdge(adj, 1, 2, 30)
    adj = addEdge(adj, 1, 3, 40)
    adj = addEdge(adj, 1, 4, 50)
    adj = addEdge(adj, 2, 3, 60)
    adj = addEdge(adj, 3, 4, 70)
    printGraph(adj, V);
     
     
     
    // This code is contributed by unknown2108
</script>

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

This article is contributed by Sahil Chhabra (akku). If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

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