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Sorting rows of matrix in descending order followed by columns in ascending order
  • Last Updated : 03 Jan, 2020

Given a matrix of distinct elements. The task is to sort the rows of matrix in descending order followed by sorting the columns in ascending order.

Examples:

Input: a[3][3] =  {{1, 2, 3},
                              {4, 5, 6}, 
                              {7, 8, 9}};
Output: 
3 2 1
6 5 4
9 8 7

Input: a[3][3] = {{3, 2, 1},
                             {9, 8, 7}, 
                             {6, 5, 4}};
Output: 
3 2 1 
6 5 4 
9 8 7

Approach:

  1. Traverse all rows one by one and sort rows in descending order using simple array sort.
  2. Convert matrix to its transpose.
  3. Again sort all rows, but this time in ascending order.
  4. Again convert matrix to its transpose.
  5. Print the final matrix.

Below is the implementation of the above approach:

C++




// C++ implementation to sort the rows
// of matrix in descending order followed by
// sorting the columns in ascending order
#include <bits/stdc++.h>
using namespace std;
  
#define MAX_SIZE 10
  
// function to sort each row of the matrix
// according to the order specified by
// descending.
void sortByRow(int mat[][MAX_SIZE], int n,
               bool descending)
{
    for (int i = 0; i < n; i++) {
        if (descending == true)
            sort(mat[i], mat[i] + n, greater<int>());
        else
            sort(mat[i], mat[i] + n);
    }
}
  
// function to find transpose of the matrix
void transpose(int mat[][MAX_SIZE], int n)
{
    for (int i = 0; i < n; i++)
        for (int j = i + 1; j < n; j++)
  
            // swapping element at index (i, j)
            // by element at index (j, i)
            swap(mat[i][j], mat[j][i]);
}
  
// function to sort the matrix row-wise
// and column-wise
void sortMatRowAndColWise(int mat[][MAX_SIZE],
                          int n)
{
    // sort rows of mat[][] in descending order
    sortByRow(mat, n, true);
  
    // get transpose of mat[][]
    transpose(mat, n);
  
    // again sort rows of mat[][] in ascending
    // order.
    sortByRow(mat, n, false);
  
    // again get transpose of mat[][]
    transpose(mat, n);
}
  
// function to print the matrix
void printMat(int mat[][MAX_SIZE], int n)
{
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++)
            cout << mat[i][j] << " ";
        cout << endl;
    }
}
  
// Driver code
int main()
{
    int n = 3;
  
    int mat[n][MAX_SIZE] = { { 3, 2, 1 },
                             { 9, 8, 7 },
                             { 6, 5, 4 } };
  
    cout << "Original Matrix:\n";
    printMat(mat, n);
  
    sortMatRowAndColWise(mat, n);
  
    cout << "\nMatrix After Sorting:\n";
    printMat(mat, n);
  
    return 0;
}


Java




// Java implementation to sort the rows
// of matrix in descending order followed
// by sorting the columns in ascending order
import java.util.*;
  
class GFG
{
  
static int MAX_SIZE = 10;
  
// function to sort each row of the matrix
// according to the order specified by
// descending.
static void sortByRow(int[][] mat, int n,
                      boolean descending)
{
    int temp = 0;
    for (int i = 0; i < n; i++)
    {
        if (descending == true)
        {
            int t = i;
            for (int p = 0; p < n; p++) 
            {
                for (int j = p + 1; j < n; j++) 
                {
      
                    if (mat[t][p] < mat[t][j]) 
                    {
                        temp = mat[t][p];
      
                        mat[t][p] = mat[t][j];
      
                        mat[t][j] = temp;
                    }
                }
            }
        
  
        else
            Arrays.sort(mat[i]);
    }
}
  
// function to find transpose of the matrix
static void transpose(int mat[][], int n)
{
    int temp = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = i + 1; j < n; j++)
        {
  
            // swapping element at index (i, j)
            // by element at index (j, i)
            temp = mat[i][j];
            mat[i][j] = mat[j][i];
            mat[j][i] = temp;
        }
    }
}
  
// function to sort the matrix row-wise
// and column-wise
static void sortMatRowAndColWise(int mat[][],
                                 int n)
{
    // sort rows of mat[][] in 
    // descending order
    sortByRow(mat, n, true);
  
    // get transpose of mat[][]
    transpose(mat, n);
  
    // again sort rows of mat[][] in 
    // ascending order.
    sortByRow(mat, n, false);
  
    // again get transpose of mat[][]
    transpose(mat, n);
}
  
// function to print the matrix
static void printMat(int mat[][], int n)
{
    for (int i = 0; i < n; i++) 
    {
        for (int j = 0; j < n; j++)
            System.out.print(mat[i][j] + " ");
        System.out.println();
    }
}
  
// Driver code
public static void main(String args[])
{
    int n = 3;
  
    int [][]mat = {{ 3, 2, 1 },
                   { 9, 8, 7 },
                   { 6, 5, 4 }};
  
    System.out.println("Original Matrix:");
    printMat(mat, n);
  
    sortMatRowAndColWise(mat, n);
  
    System.out.println("\n" + "Matrix After Sorting:");
    printMat(mat, n);
}
}
  
// This code is contributed by
// Surendra_Gangwar


Python 3




# Python 3 implementation to sort the rows
# of matrix in descending order followed by
# sorting the columns in ascending order
MAX_SIZE = 10
  
# function to sort each row of the matrix
# according to the order specified by
# descending.
def sortByRow(mat, n, descending):
  
    for i in range(n):
        if (descending == True):
            mat[i].sort(reverse = True)
        else:
            mat[i].sort()
  
# function to find transpose of the matrix
def transpose(mat, n):
  
    for i in range(n):
        for j in range(i + 1, n):
  
            # swapping element at index (i, j)
            # by element at index (j, i)
            mat[i][j], mat[j][i] = mat[j][i], mat[i][j]
  
# function to sort the matrix row-wise
# and column-wise
def sortMatRowAndColWise(mat, n):
  
    # sort rows of mat[][] in descending order
    sortByRow(mat, n, True)
  
    # get transpose of mat[][]
    transpose(mat, n)
  
    # again sort rows of mat[][] in ascending
    # order.
    sortByRow(mat, n, False)
  
    # again get transpose of mat[][]
    transpose(mat, n);
  
# function to print the matrix
def printMat(mat, n):
      
    for i in range(n):
        for j in range( n):
            print(mat[i][j], end = " ")
        print()
  
# Driver code
if __name__ == "__main__":
    n = 3
  
    mat = [[3, 2, 1 ],
           [9, 8, 7 ],
           [6, 5, 4 ]]
  
    print("Original Matrix: ")
    printMat(mat, n)
  
    sortMatRowAndColWise(mat, n)
  
    print("Matrix After Sorting:")
    printMat(mat, n)
  
# This code is contributed by ita_c


C#




// C# implementation to sort the rows
// of matrix in descending order followed
// by sorting the columns in ascending order
using System;
  
class GFG
{
static int MAX_SIZE = 10;
  
// function to sort each row of the matrix
// according to the order specified by
// descending.
static void sortByRow(int[,] mat, int n,
                      bool descending)
{
    int temp = 0;
    for (int i = 0; i < n; i++)
    {
        if (descending == true)
        {
            int t = i;
            for (int p = 0; p < n; p++) 
            {
                for (int j = p + 1; j < n; j++) 
                {
      
                    if (mat[t, p] < mat[t, j]) 
                    {
                        temp = mat[t, p];
      
                        mat[t, p] = mat[t, j];
      
                        mat[t, j] = temp;
                    }
                }
            }
        
        else
            sortByRow(mat, i, n);
    }
}
  
// function to sort each 
// row of the matrix 
static void sortByRow(int [,]mat,
                      int row, int n) 
      
    // sorting row number 'i' 
    for (int i = row; i < row + 1; i++) 
    
        for(int j = 0; j < n - 1; j++) 
        
            if(mat[i, j] > mat[i, j + 1]) 
            
              
                var temp = mat[i, j]; 
                mat[i, j] = mat[i, j + 1]; 
                mat[i, j + 1] = temp; 
                  
            
        
    
  
// function to find transpose of the matrix
static void transpose(int [,]mat, int n)
{
    int temp = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = i + 1; j < n; j++)
        {
  
            // swapping element at index (i, j)
            // by element at index (j, i)
            temp = mat[i, j];
            mat[i, j] = mat[j, i];
            mat[j, i] = temp;
        }
    }
}
  
// function to sort the matrix 
// row-wise and column-wise
static void sortMatRowAndColWise(int [,]mat,
                                 int n)
{
    // sort rows of [,]mat in 
    // descending order
    sortByRow(mat, n, true);
  
    // get transpose of [,]mat
    transpose(mat, n);
  
    // again sort rows of [,]mat in 
    // ascending order.
    sortByRow(mat, n, false);
  
    // again get transpose of [,]mat
    transpose(mat, n);
}
  
// function to print the matrix
static void printMat(int [,]mat, int n)
{
    for (int i = 0; i < n; i++) 
    {
        for (int j = 0; j < n; j++)
            Console.Write(mat[i, j] + " ");
        Console.WriteLine();
    }
}
  
// Driver code
public static void Main(String []args)
{
    int n = 3;
  
    int [,]mat = {{ 3, 2, 1 },
                  { 9, 8, 7 },
                  { 6, 5, 4 }};
  
    Console.WriteLine("Original Matrix:");
    printMat(mat, n);
  
    sortMatRowAndColWise(mat, n);
  
    Console.WriteLine("\nMatrix After Sorting:");
    printMat(mat, n);
}
}
  
// This code is contributed by 29AjayKumar


Output:

Original Matrix:
3 2 1 
9 8 7 
6 5 4 

Matrix After Sorting:
3 2 1 
6 5 4 
9 8 7

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