Ordering 2d array in lexical order - c++

Question

I have an 2d array of char, and I am trying to order them in alphabetical order. In each rows there is a word build of chars and I am trying to sort it.
I built something, but I don't understand why this is not working. If you have a solution for me, please explain what you are doing, in order to understand why I don't success.
Thanks !
char matrix[4][5] = {
{'h','e','l','l','o'},
{'r','e','a','d','y'},
{'a','p','p','l','e'},
{'p','o','i','n','t'},
};
char temp;
bool flag = false;
display(matrix);
for (int i = 0; i < 4 - 1; i++)
{
for (int rows = 0; rows < 10-1; rows++)
{
flag = false;
for (int cols = 0; cols < 5; cols++)
{
if (matrix[rows][cols] > matrix[rows + 1][cols])
{
flag = true;
break;
}
}
if (flag)
{
for (int index = 0; index < 5; index++)
{
temp=matrix[rows][index];
matrix[rows][index]=matrix[rows+1][index];
matrix[rows+1][index]=temp;
}
}
}
}

Answer 1

I will post this answer, even if it may not be what you want to do (but will be helpful for others who may want to do things this way).
Instead of sorting the 2D array, the trick is to not sort it, and instead sort an array of indices that point into the array. That is much more simpler than trying to manipulate the array itself.
Here is a very simple example:
#include <algorithm>
#include <cstring>
#include <iostream>
int main()
{
char matrix[4][5] = {
{'h','e','l','l','o'},
{'r','e','a','d','y'},
{'a','p','p','l','e'},
{'p','o','i','n','t'},
};
// create the indices
int index[] = { 0,1,2,3 };
// sort the indices based on the data in the array
std::sort(index, index + 4, [&](int n1, int n2)
{ return strncmp(matrix[n1], matrix[n2], 5) < 0; });
// Output the results
for (int i = 0; i < 4; ++i)
{
// Note how we access the original matrix using the index array
std::cout.write(matrix[index[i]], 5);
std::cout << " -- Using array at row " << index[i] << "\n";
}
}
Output:
apple -- Using array at row 2
hello -- Using array at row 0
point -- Using array at row 3
ready -- Using array at row 1
The final results show that the indices just point to the row that would be used if we want to access the array in a sorted manner. The original array was not adjusted.

Answer 2

That's it.
#include <bits/stdc++.h>
using namespace std;
char matrix[4][5] = {
{'h','e','l','l','o'},
{'r','e','a','d','y'},
{'a','p','p','l','e'},
{'p','o','i','n','t'} };
int n = 4, m = 5, k = 0;// number of rows and columns
char temp;
int main()
{
for ( int i = 0; i < n; i++ )
for ( int j = i + 1; j < n; j++ )
{
k = 0;
while ( matrix[i][k] == matrix[j][k] && k < m )
k++;
if ( k < m && matrix[i][k] > matrix[j][k] ) // ASCII code comparison
for ( int k = 0; k < m; k++ )
{
temp = matrix[i][k];
matrix[i][k] = matrix[j][k];
matrix[j][k] = temp;
}
}
for ( int i = 0; i < n; i++ )
{
for ( int j = 0; j < m; j++ )
cout << matrix[i][j];
cout << "\n";
}
}