C++ Find max(by row) and min(by column) element in array - c++

Question

I need to find the mimimum element in two-dimensional(4,4) array by row and maximum element by column and store them in another array (5,5).Maybe I did not explain properly.
That's how it should look new array (5,5):
1 2 3 4 min
1 2 3 4 min
1 2 3 4 min
m m m m 0
*m - max
So this is the first array:
int array[4][4];
int i, j;
for(i = 0; i < 4; i++) {
for(j = 0; j < 4; j++) {
cout << "\n array[" << i + 1 << "][" << j + 1 <<"]=";
cin >> array[i][j];
}
}
With this I try to find the min of each row:
int min;
for (i = 0; i<4; i++) {
min[i] = array[0][i];/*expression must have pointer-to-object type*/
for (j = 1; j<4; j++) {
if (min[i]>array[i][j])/*expression must have pointer-to-object type*/
min[i] = array[i][j];/*expression must have pointer-to-object type*/
}
}
Where I'm wrong? I can't undrestand this error "expression must have pointer-to-object type".
And with this i will try to make new array:
for(i = 0; i < 4; i++) {
for(j = 0; j < 4; j++) {
newarr[i][j]=array[i][j];
newarr[i][5]=max[i];
}
}
for(j = 0; j < 4; j++)
newarr[5][j]=min[j];
Is this okay? There is no way to check it because I just can not find the min and max.

Answer 1

int min;
min[i]
is the source of error. min is an integer variable not an integer array.
change int min to int min[4];

Answer 2

You have int min;. This variable can hold only single value and following is ill-formed min[i], as min is not an array.
Just making it an array should solve the issue: int min[4];
Also note, that first index of 2D array traditionally denotes row and second a column. And check indices usage in your loops: why do you use i as bot first and second index in different places?

Answer 3

Here is shown a straightforward approach. You may use it as a base for your program
#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <ctime>
int main()
{
const int MAX_VALUE = 100;
const size_t N = 4;
int a[N][N];
int b[N+1][N+1];
std::srand( ( unsigned int )std::time( nullptr ) );
for ( auto &row : a )
{
for ( int &x : row ) x = std::rand() % MAX_VALUE;
}
for ( const auto &row : a )
{
for ( int x : row ) std::cout << std::setw( 2 ) << x << ' ';
std::cout << std::endl;
}
std::cout << std::endl;
for ( size_t i = 0; i < N; i++ ) b[N][i] = a[0][i];
b[N][N] = 0;
for ( size_t i = 0; i < N; i++ )
{
int min = a[i][0];
for ( size_t j = 0; j < N; j++ )
{
b[i][j] = a[i][j];
if ( a[i][j] < min ) min = a[i][j];
if ( b[N][j] < b[i][j] ) b[N][j] = b[i][j];
}
b[i][N] = min;
}
for ( const auto &row : b )
{
for ( int x : row ) std::cout << std::setw( 2 ) << x << ' ';
std::cout << std::endl;
}
std::cout << std::endl;
}
The program output might look like
77 53 41 90
67 57 90 94
20 41 29 38
3 72 33 43
77 53 41 90 41
67 57 90 94 57
20 41 29 38 20
3 72 33 43 3
77 72 90 94 0
The idea is to fill the last row of the new array with values of the first row of the original array and then compare each value of the last row with a value of the current row in the current column.

Answer 4

Well that's the whole code:
#include <iostream>
using namespace std;
int main() {
int A[4][4];
int i, j;
for (i = 0; i < 4; i++)
for (j = 0; j < 4; j++) {
cout << "\n A[" << i + 1 << "][" << j + 1 << "]=";
cin >> A[i][j];
}
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++)
cout << A[i][j] << "\t";
cout << "\n";
}
{
int min[4];
for (i = 0; i < 4; i++) {
min[i] = A[0][i];
for (j = 1; j < 4; j++) {
if (min[i] > A[i][j])
min[i] = A[i][j];
}
}
int newarr[5][5];
int max[5] = { 1,2,3,4,5 };
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++) {
newarr[i][j] = A[i][j];
newarr[i][5] = max[i];
}
}
for (j = 0; j < 4; j++)
newarr[5][j] = min[j];
cout << newarr[5][j] << "\t";
cout << "\n";
}
}
I put random elements to max. Because so far I only test. But once I started my program it show correct only the first array. And where should be the new array it shows zero. Here it is the outcome of the debuging:
5 4 3 1
5 6 7 9
4 2 3 9
4 8 4 6
0