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  1. #include<bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. int main(){
  6.   map<int , vector< pair<int, int > > > adjList;  // Seems like torture xD
  7.  
  8.   /***********Explanation************
  9.   * Abstract form of a map = map< key, value >
  10.   * Here key = int,
  11.   *      Value = vector of pairs
  12.   * Key is actually a node(let's say N) of graph here and 
  13.   * Value is the vector containing all the nodes which are 
  14.   * connected to N directly.
  15.   * Why we need pair< d1, d2 > ?
  16.   * d2 = node connected to N directly.
  17.   * d1 = weight of edge between N and d2.
  18.   * For unweighted graph we can use only int instead of pair
  19.   * or we can keep value 0 for all edges if we use pair of
  20.   * int like shown below.
  21.   *************************************/
  22.   // Suppose we are given number of edges 'n' and all the edges in form of (u, v). 
  23.   // So we can use a for loop to scan inputs.
  24.  
  25.   int n;
  26.   cin >> n;
  27.   for(int i = 0 ; i < n ; i ++){
  28.     int u, v;
  29.     cin >> u >> v;
  30.     // If graph is undirected:
  31.     /* 1. */ adjList[u].push_back(make_pair(0, v));
  32.     /* 2. */ adjList[v].push_back(make_pair(0, u));
  33.     // If graph is directed from u to v
  34.     // Then no need to write 2nd statement.
  35.   }
  36.  
  37.   // Print Adjacency List
  38.  
  39.   for(map<int , vector< pair<int, int > > >::iterator it = adjList.begin() ; it != adjList.end() ; it++){
  40.     cout << it->first << " : ";
  41.     vector<pair<int, int> > neighbours = it->second;
  42.     for(int i = 0 ; i < neighbours.size() ; i++){
  43.       cout << "(" << neighbours[i].first << " " << neighbours[i].second << ")";
  44.     }
  45.     cout << endl;
  46.   }
  47.  
  48.  
  49.  
  50. }
Success #stdin #stdout 0s 16064KB
comments (?)
stdin
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7
1 5
1 2
2 5
3 4
3 2
4 5
6 4
stdout
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1 : (0 5)(0 2)
2 : (0 1)(0 5)(0 3)
3 : (0 4)(0 2)
4 : (0 3)(0 5)(0 6)
5 : (0 1)(0 2)(0 4)
6 : (0 4)
https://ideone.com/d09aHu
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
secret

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