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

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Hi there! 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:

C++

int min[4];
    for (i = 0; i<4; i++) {
        min[i] = array[0][i];
    	for (j = 1; j<4; j++) {
   			if (min[i]>array[i][j])/
   				min[i] = array[i][j];
    	}
    }

But I do not know if this code is correct. I dont know how to extract them(minimum elements).

And with this i will try to make new array:

C++

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.

Posted 13-Dec-15 6:04am

Member 12204396

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KarstenK · Answer 1 · 2015-12-13T07:43:00

It looks somehow fine, but the assignment of your min/max values are running too deeply nested. You only need it own time.

C++

for(i = 0; i < 4; i++) {
       for(j = 0; j < 4; j++) { 
           newarr[i][j]=array[i][j];
           if( j == 0) newarr[i][4]=max[i];//index error (and not so elegant)
       }
}
 
for(j = 0; j < 4; j++) 
   newarr[4][j]=min[j];//index error

newarr[4][4]=0;//last element

Really important tips to learn programming:
1. use a debugger
2. use output (TRACE)
3. write some tests with data. (Sample data with known results)

Good luck ;-)

LeumasD · Answer 2 · 2015-12-14T17:38:00

I am going to give you here a pseudo-code for a solution... you will need to translate it into a C code...

C++

Main:
    //----------
    // dim the array and intialize its elements to a random value
    //----------
    dim a[4,4]  //--define the array
    for i=0 to 3
        for j=0 to 3
            a[i,j]=random(10) //--initialize elements to random values ranging from 0 to 10... or read from a file or input stream etc.
        next
    next
    //--------
    //-- dim an array to hold the maximum values
    //-- and initialize its elements to be the top raw of the previous array
    //--------
    data ma;a[0,0],a[0,1],a[0,2],a[0,3]
    
    //-------
    //--- now this is the algorithm you are asking for
    //--- it loops through the array row by row
    //--- it intializes a temp value to the first element in the row
    //--- then in each row it loops through element by element
    //--- it finds the minimum element by reassigning the temp value
    //--- to the element if the element is smaller than the value of the element
    //--- thus it find the minimum for the row
    //--- it also compares the element to the value stored in the array of maximums
    //--- in its corresponding column... if it is larger then stores that in the array of maximums
    //--- it also prints the element and at the end of each row it prints the min
    //--- of course instead of printing you can assign to another array element etc.
    //--- finally when all is done it prints the array of maximums for each column.
    //----------
    for i=0 to 3 //-- for each row
        mi=a[i,0] //-- init the minumum value to the first element in the row
        for j=0 to 3  //-- for each element in the row
            print a[i,j];  //-- print it... or store it if you need to in another array
            if ma[j] < a[i,j] then ma[j] = a[i,j] //-- if the current element is > than the stored maximum than store it 
            if mi > a[i,j] then mi = a[i,j]  //-- if the current element is < than the minimum then store it
            if j==3 then print mi  //-- if reached the end of the row then print the minimum value ... or store it if you need to
        next j
    next i
    for i=0 to 3  //-- print the maximums array
        print ma[i];
    next
end

Member 12204396 · Answer 3 · 2015-12-13T19:49:00

Well that's the whole code:

C++

#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";

	}

}</iostream>

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

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

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