Sort Matrix in alternating ascending and descending order rowwise

Given an N x N matrix, our task is to print the row of the matrix in ascending and descending order alternatively.
Examples:

Input:
5 7 3 4 
9 5 8 2 
6 3 8 1 
5 8 9 3 
Output:
3 4 5 7 
9 8 5 2 
1 3 6 8 
9 8 5 3 
Explanation:
Here the first row is sorted in ascending order, second row sorted in descending order, third row sorted in ascending order and so on.
Input:
7 3 4 
3 8 2 
3 6 1 
Output:
3 4 7 
8 3 2 
1 3 6 
Explanation:
Here the first row is sorted in ascending order, second row sorted in descending order, third row sorted in ascending order. 

Approach to solve
To solve the problem mentioned above we iterate 0 to N and check if the ith row is even or odd, if it is even then we sort the row in ascending order otherwise sort the ith row in descending order. Return the matrix after N iterations.
Below is the implementation of the above approach:  

C++

// C++ implementation to print row of
// matrix in ascending or descending
// order alternatively

#include <stdio.h>
#define N 4

void func(int a[][N])
{

    // Iterate matrix rowwise
    for (int i = 0; i < N; i++) {

        // Sort even rows in ascending order
        if (i % 2 == 0) {
            for (int j = 0; j < N; j++) {
                for (int k = j + 1; k < N; ++k) {

                    // compare adjacent elements
                    if (a[i][j] > a[i][k]) {

                        // swap adjacent element
                        int temp = a[i][j];
                        a[i][j] = a[i][k];
                        a[i][k] = temp;
                    }
                }
            }
        }

        // Sort even rows in descending order
        else {
            for (int j = 0; j < N; j++) {
                for (int k = j + 1; k < N; ++k) {

                    // compare adjacent elements
                    if (a[i][j] < a[i][k]) {

                        // swap adjacent element
                        int temp = a[i][j];
                        a[i][j] = a[i][k];
                        a[i][k] = temp;
                    }
                }
            }
        }
    }

    // Printing the final Output
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            printf("%d ", a[i][j]);
        }
        printf("\n");
    }
}

// Driver code
int main()
{

    int a[N][N] = {
        { 5, 7, 3, 4 },
        { 9, 5, 8, 2 },
        { 6, 3, 8, 1 },
        { 5, 8, 9, 3 }
    };

    func(a);

    return 0;
}

Java

// Java implementation to print row of
// matrix in ascending or descending
// order alternatively
class GFG{

static int N = 4;

static void func(int a[][])
{
    int i, j, k;

    // Iterate matrix rowwise
    for(i = 0; i < N; i++)
    {

       // Sort even rows in ascending order
       if (i % 2 == 0)
       {
           for(j = 0; j < N; j++)
           {
              for(k = j + 1; k < N; ++k)
              {

                 // Compare adjacent elements
                 if (a[i][j] > a[i][k])
                 {

                     // Swap adjacent element
                     int temp = a[i][j];
                     a[i][j] = a[i][k];
                     a[i][k] = temp;
                 }
              }
           }
       }

       // Sort even rows in descending order
       else
       {
           for(j = 0; j < N; j++)
           {
              for(k = j + 1; k < N; ++k)
              {

                 // Compare adjacent elements
                 if (a[i][j] < a[i][k])
                 {

                     // Swap adjacent element
                     int temp = a[i][j];
                     a[i][j] = a[i][k];
                     a[i][k] = temp;
                 }
              }
           }
       }
    }

    // Printing the final Output
    for(i = 0; i < N; i++)
    {
       for(j = 0; j < N; j++)
       {
          System.out.print(a[i][j] + " ");
       }
       System.out.print("\n");
    }
}

// Driver code
public static void main (String []args)
{

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

    func(a);
}
}

// This code is contributed by chitranayal

Python3

# Python3 implementation to print row of
# matrix in ascending or descending
# order alternatively
N = 4

def func(a):

    # Iterate matrix rowwise
    for i in range(N):

        # Sort even rows in ascending order
        if i % 2 == 0:
            for j in range(N):
                for k in range(j + 1, N):

                    # Compare adjacent elements
                    if a[i][j] > a[i][k]:

                        # Swap adjacent element
                        temp = a[i][j]
                        a[i][j] = a[i][k]
                        a[i][k] = temp

        # Sort even rows in descending order
        else :
            for j in range(N):
                for k in range(j + 1, N):

                    # Compare adjacent elements
                    if a[i][j] < a[i][k]:

                        # Swap adjacent element
                        temp = a[i][j]
                        a[i][j] = a[i][k]
                        a[i][k] = temp

    # Printing the final output
    for i in range(N):
        for j in range(N):
            print(a[i][j], end = " ")
        print()

# Driver code
if __name__ == '__main__':

    a = [ [ 5, 7, 3, 4 ],
          [ 9, 5, 8, 2 ],
          [ 6, 3, 8, 1 ],
          [ 5, 8, 9, 3 ] ]

    func(a)

# This code is contributed by mohit kumar 29

C#

// C# implementation to print row of
// matrix in ascending or descending
// order alternatively
using System;
class GFG{

static int N = 4;

static void func(int[,]a)
{
    int i, j, k;

    // Iterate matrix rowwise
    for(i = 0; i < N; i++)
    {

       // Sort even rows in ascending order
       if (i % 2 == 0)
       {
           for(j = 0; j < N; j++)
           {
              for(k = j + 1; k < N; ++k)
              {

                 // Compare adjacent elements
                 if (a[i, j] > a[i, k])
                 {

                     // Swap adjacent element
                     int temp = a[i, j];
                     a[i, j] = a[i, k];
                     a[i, k] = temp;
                 }
              }
           }
       }

       // Sort even rows in descending order
       else
       {
           for(j = 0; j < N; j++)
           {
              for(k = j + 1; k < N; ++k)
              {

                 // Compare adjacent elements
                 if (a[i, j] < a[i, k])
                 {

                     // Swap adjacent element
                     int temp = a[i, j];
                     a[i, j] = a[i, k];
                     a[i, k] = temp;
                 }
              }
           }
       }
    }

    // Printing the readonly Output
    for(i = 0; i < N; i++)
    {
       for(j = 0; j < N; j++)
       {
          Console.Write(a[i, j] + " ");
       }
       Console.Write("\n");
    }
}

// Driver code
public static void Main(String []args)
{

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

    func(a);
}
}

// This code is contributed by Princi Singh

Javascript

<script>
// Javascript implementation to print row of
// matrix in ascending or descending
// order alternatively

let N = 4;

function func(a)
{

    // Iterate matrix rowwise
    for (let i = 0; i < N; i++) {

        // Sort even rows in ascending order
        if (i % 2 == 0) {
            for (let j = 0; j < N; j++) {
                for (let k = j + 1; k < N; ++k) {

                    // compare adjacent elements
                    if (a[i][j] > a[i][k]) {

                        // swap adjacent element
                        let temp = a[i][j];
                        a[i][j] = a[i][k];
                        a[i][k] = temp;
                    }
                }
            }
        }

        // Sort even rows in descending order
        else {
            for (let j = 0; j < N; j++) {
                for (let k = j + 1; k < N; ++k) {

                    // compare adjacent elements
                    if (a[i][j] < a[i][k]) {

                        // swap adjacent element
                        let temp = a[i][j];
                        a[i][j] = a[i][k];
                        a[i][k] = temp;
                    }
                }
            }
        }
    }

    // Printing the final Output
    for (let i = 0; i < N; i++) {
        for (let j = 0; j < N; j++) {
            document.write(" " + a[i][j]);
        }
        document.write("<br>");
    }
}

// Driver code

    let a = [
        [ 5, 7, 3, 4 ],
        [ 9, 5, 8, 2 ],
        [ 6, 3, 8, 1 ],
        [ 5, 8, 9, 3 ]
    ];

    func(a);

// This code is contributed by subham348.
</script>

Output:

3 4 5 7 
9 8 5 2 
1 3 6 8 
9 8 5 3

Time Complexity: O(N³)

Auxiliary Space: O(1)

Efficient approach: We can optimize the above approach by sorting any given row by using the sort() function. It will sort any given row in O(n*log(n)) time complexity. 

Steps involved in the approach:

1. Traverse through each row and check if the row is at an even number or odd.
2. If even row is there then sort it in ascending order by directly using the sort function.
3. If odd row then sort it in descending order by passing the “greater()” function in sort.

Below is the code for the above approach:

C++

// C++ implementation to print row of
// matrix in ascending or descending
// order alternatively

#include <bits/stdc++.h>
using namespace std;
#define N 4

void func(int a[][N])
{

    // Iterate matrix rowwise
    for (int i = 0; i < N; i++) {

        // Sort even rows in ascending order
        if (i % 2 == 0) {
            sort(a[i],a[i]+N);
        }

        // Sort even rows in descending order
        else {
            sort(a[i],a[i]+N,greater<int>());
        }
    }

    // Printing the final Output
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            printf("%d ", a[i][j]);
        }
        printf("\n");
    }
}

// Driver code
int main()
{

    int a[N][N] = {
        { 5, 7, 3, 4 },
        { 9, 5, 8, 2 },
        { 6, 3, 8, 1 },
        { 5, 8, 9, 3 }
    };

    func(a);

    return 0;
}

// This code is contributed by Pushpesh Raj

Output

3 4 5 7 
9 8 5 2 
1 3 6 8 
9 8 5 3 

Time Complexity: O(N²log(N))

Auxiliary Space: O(1)