CODEWITHSUNDEEP
c++multidimensional-arraymax
feco
feco

Reputation: 63

Finding the maximum value of every row in 2D array C++

I've managed to find the minimum value of every row of my 2D array with this

void findLowest(int A[][Cm], int n, int m)
{
    int min = A[0][0];
    for (int i = 0; i < n; i++)
    {
         for (int j = 0; j < m; j++)
         {
             if (A[i][j] < min)
             {
                 min = A[i][j];
             }
         }
     out << i << " row's lowest value " << min << endl;
    }
}

I'am trying to find the maximum value of every row using the same way,but it only shows me first maximum value

void findHighest(int A[][Cm], int n, int m)
{
     int max = A[0][0];
     for (int i = 0; i < n; i++)
     {
         for (int j = 0; j < m; j++)
         {
             if (A[i][j] > max)
             {
                max = A[i][j];
             }
         }
     out << i << " row's highest value " << max << endl;
     }
}

I can't find what's wrong with the second function and why is it only showing me the first maximum value it finds. Any help ?

Upvotes: 5

Views: 58911

Answers (5)

user11358360
user11358360

Reputation: 1

{

int i,j;

int arr[4][2]={(1,2),(3,4),(5,6),(7,8)};
int max;
max=arr[0][0];

for( int i=0; i<4; i++)
{
    for(int j=0; j<2; j++)
    {
        if(max<arr[i][j])
        {
            max=arr[i][j];

        }

    }

}

int min;
min=arr[0][0];

for(int i=0; i<4; i++)
{
    for(int j=0; j<2; j++)
    {
        if(min>arr[i][j])
        {
            min=arr[i][j];
        }
    }
}

cout<<"maximum number is:"<<max;
cout<<endl;
cout<<"Minimum Number is:"<<min;

}

Upvotes: 0

Dimitrios Bouzas
Dimitrios Bouzas

Reputation: 42899

If your compiler supports C++11, for concrete arrays you could use the following alternative, that's based on std::minmax_element:

template<typename T, std::size_t N, std::size_t M>
void
minmax_row(T const (&arr)[N][M], T (&mincol)[N], T (&maxcol)[N]) {
  for(int i(0); i < N; ++i) {
    auto mnmx = std::minmax_element(std::begin(arr[i]), std::end(arr[i]));
    if(mnmx.first != std::end(arr[i]))  mincol[i] = *(mnmx.first);
    if(mnmx.second != std::end(arr[i])) maxcol[i] = *(mnmx.second);
  }
}

Live Demo

Upvotes: 4

The_Novice
The_Novice

Reputation: 11

As mentioned your code only shows the maximum element in the whole array. Here is the code which will help you.

 void findHighest(int A[][Cm], int n, int m)
 {
    int max[n];
    max[0]=A[0][0];
    for (int i = 0; i < n; i++)
  {
      for (int j = 0; j < m; j++)
      {
         if (A[i][j] > max[i])
         {
            max[i] = A[i][j];
         }
     }
  cout << i << " row's highest value " << max[i] << endl;
 }
}

Upvotes: 1

vitaut
vitaut

Reputation: 55554

Both functions return the result (maximum or minimum) for the whole array rather than each row, because you set max once rather than once per row. You can get the result for each row as follows:

void findHighest(int A[][Cm], int n, int m)
{
     for (int i = 0; i < n; i++)
     {
         int max = A[i][0];
         for (int j = 1; j < m; j++)
         {
             if (A[i][j] > max)
             {
                max = A[i][j];
             }
         }
         // do something with max
     }
}

or, even better, use the standard library function max_element:

void findHighest(int A[][Cm], int n, int m)
{
     if (m <= 0) return;
     for (int i = 0; i < n; i++)
     {
         int max = *std::max_element(A[i], A[i] + m);
         // do something with max
     }
}

This should give you all values which is easy to check:

#include <algorithm>
#include <iostream>

enum { Cm = 2 };

void findHighest(int A[][Cm], int n, int m) {
  if (m <= 0) return;
  for (int i = 0; i < n; i++) {
    int max = *std::max_element(A[i], A[i] + m);
    std::cout << max << " ";
  }
}

int main() {
  int A[2][2] = {{1, 2}, {3, 4}};
  findHighest(A, 2, 2);
}

prints 2 4.

Upvotes: 5

user1196549
user1196549

Reputation:

Your test data is guilty for not clearly showing you the defect.

The row minima occur in decreasing values, so that they get updated on every row.

And the row maxima also occur in decreasing values, so that the first one keeps winning.

As others pointed, your function finds the global minimum/maximum, no the per-row extrema.

Move the initialization of the min/max variable inside the outer loop.

Upvotes: 2

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