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Storing integers values from file into a vectors of vector


Storing integers values from file into a vectors of vector

By : J Edwin Monsalve
Date : October 22 2020, 06:10 AM
I hope this helps . Each iteration of your loop needs to do two things:
create a new inner vector in links add the three elements to the newly created inner vector
code :
while (...)
{
#if 0
    // create new inner vector (C++17 version)
    auto& inner = links.emplace_back();
#else
    // create new inner vector (C++11 version)
    links.emplace_back();
    auto& inner = links.back();
#endif

    // insert elements
    inner.push_back(a);
    inner.push_back(b);
    inner.push_back(c);
}


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OpenCV storing vectors of vectors of points vector<vector<Point> >

OpenCV storing vectors of vectors of points vector<vector<Point> >


By : Hamza Deutz
Date : March 29 2020, 07:55 AM
I wish did fix the issue. For the moment, I solved this by just not using OpenCV's FileStorage. Here is what I did for storing a vector of vector of Point since there are good routines for printing the vectors.
code :
bool writeVectorVectorPoint(string fname, vector<vector<Point> > vvP)
{
  ofstream fsOut;
  vector<vector<Point> >::iterator p;

  fsOut.open(fname.c_str());
  if(fsOut.fail())
  {
    cout << "Failed to open " << fname << endl;
    return(false);
  }
  for(p = vvP.begin(); p != vvP.end(); p++)
  {
    fsOut << (*p) << endl;
  }
  fsOut.close();
  return(true);
}
bool readVectorVectorPoint(string fname, vector<vector<Point> >& vvP)
{
  ifstream fsIn;
  fsIn.open(fname.c_str());
  if(fsIn.fail())
  {
    cout << "Failed to open: " << fname << endl;
    return(false);
  }
  Point pt;
  vector<Point> vPt;
  vector<Point>::iterator p;
  string line;
  while(getline(fsIn, line))
  {
    cout << line << endl;
    string ptStr;
    stringstream s(line.substr(1,line.size()-1));
    vPt.clear();
    while(getline(s, ptStr, ';'))
    {
      stringstream s1(ptStr);
      string lastStr;
      getline(s1, lastStr, ',');
      pt.x = atoi(lastStr.c_str());
      getline(s1, lastStr, ',');
      pt.y = atoi(lastStr.c_str());
      vPt.push_back(pt);
    }
    vvP.push_back(vPt);
  }

  fsIn.close();
  return(true);
}
Reading a text file (with integers) row by row and storing each row as a vector (C++)

Reading a text file (with integers) row by row and storing each row as a vector (C++)


By : R.thakur
Date : March 29 2020, 07:55 AM
wish helps you I'm working on graph theory problems and using the adjacency list implementation. I have long text files which represent the adjacency list of graphs with N>100 vertices. , This small example, should show one way of doing this:
code :
#include <vector>
#include <sstream>
#include <iostream>
#include <string>
#include <iterator>
//...
int main()
{
    // use a typedef to simplify things a bit 
    typedef std::vector<int> Int1D;
    typedef std::vector<Int1D> Int2D;

    // declare the adjacency list
    Int2D adjList;

    std::string line;
    std::ifstream infile;
    //...
    //..assume that infile has been opened successfully
    //...
    while (std::getline(infile, line))
    {
       // use a string stream to help parse the ints
       std::istringstream strm(line);
       int n;

       // add an empty row
       adjList.push_back(Int1D());

       // now fill in the last row we added by reading in the ints
       while (strm >> n)
          adjList.back().push_back(n);
    }

    // output results
    for (size_t i = 0; i < adjList.size(); ++i)
    {
       std::copy(adjList[i].begin(), adjList[i].end(), std::ostream_iterator<int>(std::cout, " "));
       std::cout << '\n';
    }
}
Sum of vector of vectors of vectors ... of integers

Sum of vector of vectors of vectors ... of integers


By : Tejaswin Renugunta
Date : March 29 2020, 07:55 AM
it helps some times Reading your error message. It looks like your functions are in a separate compilation unit from main.cpp. If your functions are in a .h file, #include the header file in main.cpp.
I would suggest using the template specialization declaration:
code :
template<>
int sumAllElements(std::vector<int> v)
{
 ...   
}
Storing and reading integers into a vector array from .txt file

Storing and reading integers into a vector array from .txt file


By : user1616444
Date : March 29 2020, 07:55 AM
it should still fix some issue Never use both stdio and iostream. For files it'd be better if you used fstream, like this:
code :
#include <fstream>

ifstream fin("sample.txt");

int number;

while(fin >> number)
{
    numArray.push_back(number);
}
Storing Matrix information in STL vector. Which is better vector or vector of vectors?

Storing Matrix information in STL vector. Which is better vector or vector of vectors?


By : Evgeny Lisin
Date : March 29 2020, 07:55 AM
I wish this help you Have you considered using an off-the-shelf matrix representation such as boost's instead of reinventing the wheel?
If you have a lot of empty rows for example, using the nested representation could save a lot of space. Unless you have specific information in actual use cases showing one way isn't meeting your requirements, code the way that's easiest to maintain and implement properly.
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