Question

I am trying to make multi-weighted graphs.
Input is to be made in following way

1. Firstly user number of vertex user want and
2. The ith line of a programmer’s map contains details of the vertex
   directly accessible from room i . for ex

5
a 2 // (vertex 1 is connected to vertex 2 by edge having weight ‘a’)
t 5 r 4 // (vertex 2 is connected to vertex 4 an by edge having weight ‘t’and’r’)
a 4
r 2 t 3
b 5 i 5 o 5

#include <iostream>
#include <vector>
#include <sstream>
using namespace std;
struct maps{
 vector<char> weight;   //for storing multiple-edge and self-loop![enter image description here][1]
};
void input_edge(int n,maps m[10][10])
{
 std::string user_input;
 std::istringstream iss(user_input);
 char letter;// for making tokens 
 int index; // for making tokens
 int i;
 for(i=1;i<=n;i++)
{ std::getline(std::cin, user_input);
  while (iss >> letter >> index)
  m[i][index].weight.push_back(letter);
}
}
int main()
{ int n;//no.of vertex user want to make graph
  cin>>n;
  cin.ignore(1000,'\n');
  maps m1[10][10];
  input_edge(n,m1);
  int i,j; 
  for(i=1;i<=n;i++)
  for(j=1;j<=n;j++)
  {cout<<"no of edge between vertex"<<i<<' '<<"and"<<' '<<j<<':'<<m1[i][j].weight.size()<<endl;}//to find no of edge between 2 vertex
} 

but i am getting incorrect outputs.please tell how to fix it..

[1]: https://i.stack.imgur.com/sTgeD.png

Answer 1

You don’t quite understand the use of istringstream. On this line std::istringstream iss(user_input); you fill in all the content you will read from the input string stream. From then on nevermind how many things you read in std::getline(std::cin, user_input); you never change the contents of iss, meaning that the input string stream will never serve you anything but nulls. Change your code like that:

void input_edge(int n,maps m[10][10])
{
 std::string user_input;

 char letter;// for making tokens 
 int index; // for making tokens
 int i;
 for(i=1;i<=n;i++)
{ std::getline(std::cin, user_input);
  std::istringstream iss(user_input);
  while (iss >> letter >> index)
  m[i][index].weight.push_back(letter);
}

And see if there is any difference.