Thread: Reading a text file to a vector

Hello!
I wanted to use vectors to read my input text file.
I dont know what is going wrong in the code.
Can anyone comment?
thanks

Code:

#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
#include <vector>
using namespace std;

int main()
{
  
  FILE *fp;
  int  s = 0;
  char  c;
  fp = fopen("10_1.txt","r");    // reading the file
  while((c=fgetc(fp))!=EOF) 
    {
      if(c=='\n')
	s = s + 1;
    }
  
  vector<int>myints1(s);
  vector<int>myints2(s);
  for (i = 0; i <s;i++){
    scanf("%d",&myints1[i]);
    printf("%d",myints1[i]);
  }
  return 0;
}

I am able to read my file using the vectors as

Code:

 vector<int> v1;
  vector<int> v2;
  vector<int> v(30);                           
  vector<int>::iterator it;
  fp = fopen("10_1.txt","r");  
  
  while(fgets(buffer, 49, fp) != NULL)
    {
      if (sscanf(buffer, "%d %d", &val1, &val2) != 2) 
	{
	  printf("Error\n");
	}
      else
	{
	  v1.push_back(val1);
	  v2.push_back(val2);
	}
    }
  for(unsigned int i=0;i<v1.size();i++)
    {
       printf("%d %d\n", v1[i], v2[i]);
    }

But I still have issues of reading the columns and comparing them.
My file has 2 columns as
1 4
2 3
3 2
4 5

I want to go through the first column ans then the second, if there is a value that is present int the second column but not in first I want to get that (in this case value 5)
and want to swap the values.

I tried with for loop but dint work for me.
Any suggestions???

Want to swap ... which values?

in this particular case, if 5 is not in the first column then make it the first entry and the associated value the secon

the the file will look like
1 4
2 3
3 2
4 5

1 4
2 3
3 2
5 4

thanks....
I worked it out.

But I have a function that gives me the intersection of 2 vectors. But I dont know the return types of this function.
I want to pass the value returned by the Intersection function to another function but get an error as
error: invalid conversion from 'int (*)()' to 'int'

The Intersection function is

Code:

int Intersection()
{
  
  set<int>::iterator it;
  set<int>::iterator iterr;
  sort (v1.begin(), v1.begin()+v1.size());  
  sort (v2.begin(), v2.begin()+v2.size());  
  set_intersection (v1.begin(), v1.begin()+v1.size(),v2.begin(), v2.begin()+v2.size(), v.begin());
  set<int> vset(v.begin(), v.end());
  set<int>newset(v1.begin(),v1.end());
  intersection = int(vset.size());
 
  printf("the intersection cardinality is %d\n", intersection);
  for (iterr=newset.begin(); iterr!=newset.end(); ++iterr){
    bool flag = false;
    for (it=vset.begin(); it!=vset.end(); ++it)
      {   
	if (*iterr == *it)
	  {
	    flag = true;    
	  }
      }
    if (!flag)
      printf("\nThe actual values are %d \n", *iterr);
  }
  printf("\n");
  return *iterr;
  
}

It returns 3 values as 1, 5, 7.

I want to pass these values into another function. say Convert defined as
void Convert(int position)
but not able to

If you want to return a set, then return a set.

As to the error, by the time you reach the end of your function, iterr == newset.end(), meaning it's not a valid iterator, meaning trying to dereference it gives bad things.