Btukfyl

I have a project that told me to import a csv file and then sort it (The file contains million of numbers). I googled for a merge sort source code and found this, i tried it and the sorting is working. (I compiled this code in ubuntu with g++ via Virtual Box).

#include<iostream>

#include<vector>



using namespace std;



void print(vector<int> v)

{

  for(int i = 0; i < v.size(); i++) cout << v[i] << " ";

  cout << endl;

}



vector<int> merge(vector<int> left, vector<int> right)

{

   vector<int> result;

   while ((int)left.size() > 0 || (int)right.size() > 0) {

      if ((int)left.size() > 0 && (int)right.size() > 0) {

         if ((int)left.front() <= (int)right.front()) {

            result.push_back((int)left.front());

            left.erase(left.begin());

         } 

   else {

            result.push_back((int)right.front());

            right.erase(right.begin());

         }

      }  else if ((int)left.size() > 0) {

            for (int i = 0; i < (int)left.size(); i++)

               result.push_back(left[i]);

            break;

      }  else if ((int)right.size() > 0) {

            for (int i = 0; i < (int)right.size(); i++)

               result.push_back(right[i]);

            break;

      }

   }

   return result;

}



vector<int> mergeSort(vector<int> m)

{

   if (m.size() <= 1)

      return m;



   vector<int> left, right, result;

   int middle = ((int)m.size()+ 1) / 2;



   for (int i = 0; i < middle; i++) {

      left.push_back(m[i]);

   }



   for (int i = middle; i < (int)m.size(); i++) {

      right.push_back(m[i]);

   }



   left = mergeSort(left);

   right = mergeSort(right);

   result = merge(left, right);



   return result;

}



int main()

{

   vector<int> v;



   v.push_back(38);

   v.push_back(27);

   v.push_back(43);

   v.push_back(3);

   v.push_back(9);

   v.push_back(82);

   v.push_back(10);



   print(v);

   cout << "------------------" << endl;



   v = mergeSort(v);



   print(v);

}

But when i insert the code to import the csv file, it only read the file and the sorting is not running, am i placed it wrong? Here is my code :

#include <fstream>

#include <iostream>

#include <vector>

#include <string>

#include <stdio.h>

#include <cstdlib>

#include <stdlib.h>



using namespace std;



const int jumlahData = 999999;

double data[jumlahData] = {0};



void loadData(const char* namaFile) {

    string line;

    ifstream myfile (namaFile);



    if (myfile.is_open()) {

        int counter = 0;

        while (getline(myfile, line, ',')) {

            //cout << line << 'n';

            data[counter] = stod(line);

            counter++;

        }

        myfile.close();

    }

}



void print(vector<int> v)

{

  for(int i = 0; i < v.size(); i++) cout << v[i] << " ";

  cout << endl;

}



vector<int> merge(vector<int> left, vector<int> right)

{

   vector<int> result;

   while ((int)left.size() > 0 || (int)right.size() > 0) {

      if ((int)left.size() > 0 && (int)right.size() > 0) {

         if ((int)left.front() <= (int)right.front()) {

            result.push_back((int)left.front());

            left.erase(left.begin());

         } 

   else {

            result.push_back((int)right.front());

            right.erase(right.begin());

         }

      }  else if ((int)left.size() > 0) {

            for (int i = 0; i < (int)left.size(); i++)

               result.push_back(left[i]);

            break;

      }  else if ((int)right.size() > 0) {

            for (int i = 0; i < (int)right.size(); i++)

               result.push_back(right[i]);

            break;

      }

   }

   return result;

}



vector<int> mergeSort(vector<int> m)

{

   if (m.size() <= 1)

      return m;



   vector<int> left, right, result;

   int middle = ((int)m.size()+ 1) / 2;



   for (int i = 0; i < middle; i++) {

      left.push_back(m[i]);

   }



   for (int i = middle; i < (int)m.size(); i++) {

      right.push_back(m[i]);

   }



   left = mergeSort(left);

   right = mergeSort(right);

   result = merge(left, right);



   return result;

}



int main()

{

   vector<int> v;



   loadData("dataDemo.csv");



   print(v);

   cout << "------------------" << endl;



   v = mergeSort(v);



   print(v);

}

your loadData("dataDemo.csv"); call does not writes to a previously declared local vector<int> v;. Your vector v has no elements. You need to write a method that populates vector v based on the contents of double data[jumlahData]
namely..

int main()

{

   vector<int> v;



   loadData("dataDemo.csv");

   populateVectorWithData(v, data); //TODO implement me

   print(v);

   cout << "------------------" << endl;



   v = mergeSort(v);



   print(v);

}

As others have pointed out, you are not sorting the actual data that you read in. This can be easily be solved by returning a count of the data-points you read-in.

A better approach, one that I suspect you are trying, is to send a reference of the vector from main to loadData and push_back the data on the vector. Furthermore, it is advisable to use your implementations provided libraries when possible. In other words, do not reinvent the wheel and just use <algorithm> instead of your own or someone else's sorting algorithm. It helps prevent nasty bugs.

int main()

{

  //return the count of integers read into data in loadData()

  //also change the vector & array types to be consistent, please!

  std::vector<int> v (data, loadData("dataDemo.csv");



  print(v);   //print the loaded vector

  cout << "------------------" << endl;



  std::sort(v.begin(), v.end());  // using <algorithm> (̶i̶t̶'̶s̶ ̶q̶u̶i̶c̶k̶s̶o̶r̶t̶)̶



  print(v);

}