Parsing an edge list into a vector of structs

Question

I am having a hard time parsing an edge list from a text file in c++. The edge list is in the following format:

*Edgeslist
1 6487
2 6488 6489 6490 6491 6492 6493 6494 6495 6496
3 6497 6498 6499 6500 6501 6502 6503 6504 6505
4 6506 6507 6508
5 6509 6510 6511
6 6512 6513 6514 6515
7 6516
8 6517 6518
9 6519 6520
10 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535
11 6566

My vector is a vector of structs that is defined here

struct Edge{
int character;
int edges[16];
};

The first number of each line should be read into the character integer and the rest should be read into the edges array. I have tried a few for loops, and currently working on a lengthy while loop with if statements for each number of possible integers to go into the array (max of 15 integers per line after the first number). Here is a part of my implementation so you can see what I am attempting.

while(std::getline(input, line))
{
  int a, b, c, d, e, f, g, h, i, j, k, l, m, n, o;
  std::stringstream ss(line);
  if ( ss >> a)
  {
       std::cout << "1 " << a << "\n";
  }
  if ( ss >> a >> b)
  {
       std::cout << "2 " << a << " " << b << "\n";
  }
  if ( ss >> a >> b >> c)
  {
       std::cout << "3 " << a << " " << b << " " << c << "\n";
  }
  if ( ss >> a >> b >> c >> d)
  {
       std::cout << "4 " << a << " " << b << " " << c << " " << d << "\n";
  }

I'll end it there but it does go on for awhile until it covers every possible line. At the moment I am just trying to figure out the basic logic to parse this text file.

Answer 1

You should split your string into substrings at whitespaces. Details are explained here.

After that, you just cast your substrings to appropiate type.

Answer 2

std::stringstream ss(line);
ss >> character;
unsigned int n=0;
while(ss >> edges[n])
{
  ++n;
}

(One could make this a little shorter, but that would make it less readable.)

Answer 3

You have tagged this as C++.

I would recommend you add an initializer if you must continue with pod ...

struct Edge
{
   int character;
   int edges[16];
   //  more data attributes

   // use ctor to initialize these values
   Edge(void) :
      character (0)
      // edges[16] 
   { 
      for (int i=0; i<16; ++i)
         edges[i] = 0;
   }


   // use dtor to clear them
  ~Edge(void)
   { 
      for (int i=0; i<16; ++i)
         edges[i] = 0;
      character = 0;
      // ...
   }

};

I suspect you will also need a count of how many edges have currently been in installed (or perhaps call it nextIn).

---

The fundamentally important signature of C++ code is the preferred use of objects-defined-by-a-class. I recommend you consider:

struct Edge
{
   int character;               // poor name choice
   std::vector<int> edges;      // << use vector, not array

   // use ctor to initialize these values
   Edge(void) :
      character (0)
      // edges   // default ctor does what you need
   { 
   }

   ~Edge(void) {
       // edges default dtor does what you need
       character = 0;
    }
};

The std::vector reduces your work to read arbitrary counts of values.

// Typical input:
// 3 6497 6498 6499 6500 6501 6502 6503 6504 6505
// 4 6506 6507 6508

#include <iostream>
#include <iomanip>
#include <sstream>
#include <vector>

struct Edge
{
   int character;               // <<< poor name choice
   std::vector<int> edges;      // <<< use vector, not array

   // use ctor to initialize these values
   Edge(void) :
      character (0)
      // edges  default ctor does what you need
      {
      }

   ~Edge(void) {
      // edges default dtor does what you need
      character = 0;
   }

   bool ok(void) {
      /*tbd - count errors? size check? */
      return(true);
   };

   void load(std::string line)
      {
         // typical input line
         // 3 6497 6498 6499 6500 6501 6502 6503 6504 6505
         // 4 6506 6507 6508

         std::stringstream ss(line+' ');
         // padding at end ---------^----because ss.eof() sooner than I expected

         //debug only
         //std::cout << "  in: (" << std::setw(3) << line.size() << ") 
         //          << line << std::endl;

         // process one work buff
         do {

            ss >> character; // read 1st int of line

            if (ss.eof()) break;

            if (ss.bad()) {
               // maybe invalid integer format
               std::cerr << "bad input: " << line << std::endl;
               // tbd - error count?
               break;
            }

            // process 1 or more entries for edge.vector from line
            do {

               int edgeVal = 0;

               ss >> edgeVal;

               if (ss.eof()) break;

               if (ss.bad()) {
                  // maybe invalid integer format
                  std::cerr << "bad input: " << line << std::endl;
                  // tbd - error count?
                  break;
               }

               // additional edgeVal validations?

               edges.push_back(edgeVal);  // fill in one value to edge vector

               // add validation here if edges.size() has an upper limit
               // tbd - error count?

            } while (1); // // process 1 or more entries to vector from line
         } while(1); // one work buff

         // debug only
         dump();

      }  // void load(std::stringstream& ss, std::string line)

   // for debug 
   void dump()
      {
         std::cout << "dump: (" << std::setw(3) << edges.size()
                   << ")  " << character << " ";

         for (size_t i=0; i<edges.size(); ++i)
            std::cout << edges[i] << " ";
         std::cout << std::endl;
      }

};  // struct Edge()



int t237(void)
{
   std::vector<Edge> edgeVec;

   // file processing at outer scope
   do {

      std::string line; // work buff

      (void)std::getline(std::cin, line);

      if(std::cin.eof()) break;

      std::stringstream ss(line);

      Edge temp; // a work buff

      temp.load(line); // <<< load method for Edge (part of Edge)

      // not sure where to put all the Edge objects
      // temporarily, use edgeVec;
      if (temp.ok())   // add flag check that edgeVec had no errors
         edgeVec.push_back(temp);
      else
         /*tbd*/{};  // error in temp ... discard it? report it?

   } while (1);

   // tbd - how return vector and file status

   return (0);
}

---- update

ss.eof() occurring before I expected ... added "padding at end" added dump() debug method, added debug cout of input line

minimal testing complete