CODEWITHSUNDEEP
c++arraysfile
Madeline Alston
Madeline Alston

Reputation: 11

Subtracting min from a 2D array

So I'm trying to read a 2D array from a file, find the smallest number in that array, and then subtract that number from each element in the array. my file "ola4.dat" contains: 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 I made the file so it'd be easy to spot that it was working because it should print a 0 and all 1's. For some reason my output is: 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Can anyone please tell me where I'm am going wrong?

Thanks 

#include <iostream>
#include <iomanip> 
#include <fstream>

using namespace std; 

int main ()
{

   int numbers[5][10]; //array
   int count 0; 
   ifstream myIn; //file name for ola4.dat
   int lowest; 

   myIn.open("ola4.dat"); 

//loop to read in 2D array
   for(int i = 0; i < 5; i++){
      for(int j = 0; j < 10; j++){

           myIn >> numbers[i][j]; 
         }
    }

    lowest = numbers[0][0]; //setting lowest to first element in array 

//loop to find lowest 
    for (int i = 0; i <5; i++){

       for (int j = 0; j < 10; j++){

           if(numbers[i][j] < lowest)
            lowest = numbers[i][j]; 
          }
     }

//loop to subtract lowest from each element in the array
    for (int i = 0; i <5; i++){

        for (int j = 0; j < 10; j++){

           numbers[i][j] - lowest; 
          }
     }

//loop to print each element in the array
    for (int i = 0; i <5; i++){

       for (int j = 0; j <10; j++){

           cout << numbers[i][j] <<' '; 
          }
       cout << endl; 
    }

Upvotes: 1

Views: 389

Answers (2)

Abhishek Kulkarni
Abhishek Kulkarni

Reputation: 1767

Try this below :

#include <iostream>
#include <iomanip> 
#include <fstream>

using namespace std; 

int main ()
{

   int numbers[5][10]; //array
   int count 0; 
   ifstream myIn; //file name for ola4.dat
   int lowest; 

   myIn.open("ola4.dat"); 

//loop to read in 2D array
   for(int i = 0; i < 5; i++){
      for(int j = 0; j < 10; j++){

           myIn >> numbers[i][j]; 
         }
    }

    lowest = numbers[0][0]; //setting lowest to first element in array 

//loop to find lowest 
    for (int i = 0; i <5; i++){

       for (int j = 0; j < 10; j++){

           if(numbers[i][j] < lowest)
            lowest = numbers[i][j]; 
          }
     }

//loop to subtract lowest from each element in array
    for (int i = 0; i <5; i++){

        for (int j = 0; j < 10; j++){

           numbers[i][j] -= lowest; 
          }
     }

//loop to print each element in array
    for (int i = 0; i <5; i++){

       for (int j = 0; j <10; j++){

           cout << numbers[i][j] <<' '; 
          }
       cout << endl; 
    }

Upvotes: 0

R Sahu
R Sahu

Reputation: 206717

The line

numbers[i][j] - lowest;

doesn't do what you want to do. It just evaluates the term and discards it.

You need

numbers[i][j] -= lowest;

or

numbers[i][j] = numbers[i][j] - lowest;

I would suggest using the first form. It's simpler and less error prone.

It's not clear to me why you would get only 5 numbers per row in the output. You should get 10 numbers per row.

Upvotes: 1

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