Print matrix in zig-zag fashion

Given a matrix of 2D array of n rows and m columns. Print this matrix in ZIG-ZAG fashion as shown in figure. 

Example:

Input: 
1 2 3
4 5 6
7 8 9
Output: 
1 2 4 7 5 3 6 8 9

Approach of C++ code
The approach is simple. Just simply iterate over every diagonal elements one at a time and change the direction according to the previous match. 

Approach of Python3 code
This approach is simple. While travelling the matrix in the usual fashion, on basis of parity of the sum of the indices of the element, add that particular element to the list either at the beginning or at the end if sum of i and j is either even or odd respectively. Print the solution list as it is.

Implementation:

C++

/* C++ Program to print matrix in Zig-zag pattern*/
#include <iostream>
using namespace std;
#define C 3

// Utility function to print matrix
// in zig-zag form
void zigZagMatrix(int arr[][C], int n, int m)
{
    int row = 0, col = 0;

    // Boolean variable that will true if we
    // need to increment 'row' value otherwise
    // false- if increment 'col' value
    bool row_inc = 0;

    // Print matrix of lower half zig-zag pattern
    int mn = min(m, n);
    for (int len = 1; len <= mn; ++len) {
        for (int i = 0; i < len; ++i) {
            cout << arr[row][col] << " ";

            if (i + 1 == len)
                break;
            // If row_increment value is true
            // increment row and decrement col
            // else decrement row and increment
            // col
            if (row_inc)
                ++row, --col;
            else
                --row, ++col;
        }

        if (len == mn)
            break;

        // Update row or col value according
        // to the last increment
        if (row_inc)
            ++row, row_inc = false;
        else
            ++col, row_inc = true;
    }

    // Update the indexes of row and col variable
    if (row == 0) {
        if (col == m - 1)
            ++row;
        else
            ++col;
        row_inc = 1;
    }
    else {
        if (row == n - 1)
            ++col;
        else
            ++row;
        row_inc = 0;
    }

    // Print the next half zig-zag pattern
    int MAX = max(m, n) - 1;
    for (int len, diag = MAX; diag > 0; --diag) {

        if (diag > mn)
            len = mn;
        else
            len = diag;

        for (int i = 0; i < len; ++i) {
            cout << arr[row][col] << " ";

            if (i + 1 == len)
                break;

            // Update row or col value according
            // to the last increment
            if (row_inc)
                ++row, --col;
            else
                ++col, --row;
        }

        // Update the indexes of row and col variable
        if (row == 0 || col == m - 1) {
            if (col == m - 1)
                ++row;
            else
                ++col;

            row_inc = true;
        }

        else if (col == 0 || row == n - 1) {
            if (row == n - 1)
                ++col;
            else
                ++row;

            row_inc = false;
        }
    }
}

// Driver code
int main()
{
    int matrix[][3] = { { 1, 2, 3 },
                        { 4, 5, 6 },
                        { 7, 8, 9 } };
    zigZagMatrix(matrix, 3, 3);

    return 0;
}

Java

/* Java Program to print matrix in Zig-zag pattern*/
class GFG {
  static final int C = 3;

  // Utility function to print matrix
  // in zig-zag form
  static void zigZagMatrix(int arr[][], int n, int m) {
    int row = 0, col = 0;

    // Boolean variable that will true if we
    // need to increment 'row' value otherwise
    // false- if increment 'col' value
    boolean row_inc = false;

    // Print matrix of lower half zig-zag pattern
    int mn = Math.min(m, n);
    for (int len = 1; len <= mn; ++len) {
      for (int i = 0; i < len; ++i) {
        System.out.print(arr[row][col] + " ");

        if (i + 1 == len)
          break;
        // If row_increment value is true
        // increment row and decrement col
        // else decrement row and increment
        // col
        if (row_inc) {
          ++row;
          --col;
        } else {
          --row;
          ++col;
        }
      }

      if (len == mn)
        break;

      // Update row or col value according
      // to the last increment
      if (row_inc) {
        ++row;
        row_inc = false;
      } else {
        ++col;
        row_inc = true;
      }
    }

    // Update the indexes of row and col variable
    if (row == 0) {
      if (col == m - 1)
        ++row;
      else
        ++col;
      row_inc = true;
    } else {
      if (row == n - 1)
        ++col;
      else
        ++row;
      row_inc = false;
    }

    // Print the next half zig-zag pattern
    int MAX = Math.max(m, n) - 1;
    for (int len, diag = MAX; diag > 0; --diag) {

      if (diag > mn)
        len = mn;
      else
        len = diag;

      for (int i = 0; i < len; ++i) {
        System.out.print(arr[row][col] + " ");

        if (i + 1 == len)
          break;

        // Update row or col value according
        // to the last increment
        if (row_inc) {
          ++row;
          --col;
        } else {
          ++col;
          --row;
        }
      }

      // Update the indexes of row and col variable
      if (row == 0 || col == m - 1) {
        if (col == m - 1)
          ++row;
        else
          ++col;

        row_inc = true;
      }

      else if (col == 0 || row == n - 1) {
        if (row == n - 1)
          ++col;
        else
          ++row;

        row_inc = false;
      }
    }
  }
  // Driver code
  public static void main(String[] args) {
    int matrix[][] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    zigZagMatrix(matrix, 3, 3);
  }
}
// This code is contributed by Anant Agarwal.

Python3

# Program to print matrix in Zig-zag pattern

matrix =[
            [ 1, 2, 3,],
            [ 4, 5, 6 ],
            [ 7, 8, 9 ],
        ]
rows=3
columns=3

solution=[[] for i in range(rows+columns-1)]

for i in range(rows):
    for j in range(columns):
        sum=i+j
        if(sum%2 ==0):

            #add at beginning
            solution[sum].insert(0,matrix[i][j])
        else:

            #add at end of the list
            solution[sum].append(matrix[i][j])


# print the solution as it as
for i in solution:
    for j in i:
        print(j,end=" ")

C#

// C# Program to print matrix
// in Zig-zag pattern
using System;

class GFG {
    static int C = 3;

    // Utility function to print
    // matrix in zig-zag form
    static void zigZagMatrix(int[, ] arr, int n, int m)
    {
        int row = 0, col = 0;

        // Boolean variable that will
        // true if we need to increment
        // 'row' valueotherwise false-
        // if increment 'col' value
        bool row_inc = false;

        // Print matrix of lower half
        // zig-zag pattern
        int mn = Math.Min(m, n);
        for (int len = 1; len <= mn; ++len) {
                for (int i = 0; i < len; ++i) {

                Console.Write(arr[row, col] + " ");

                if (i + 1 == len)
                    break;

                // If row_increment value is true
                // increment row and decrement col
                // else decrement row and increment
                // col
                if (row_inc) {
                    ++row;
                    --col;
                }
                else {
                    --row;
                    ++col;
                }
            }

            if (len == mn)
                break;

            // Update row or col value
            // according to the last
            // increment
            if (row_inc) {
                    ++row;
                    row_inc = false;
            }
            else {
                ++col;
                row_inc = true;
            }
        }

        // Update the indexes of row
        // and col variable
        if (row == 0) {
            if (col == m - 1)
                ++row;
            else
                ++col;
            row_inc = true;
        }
        else {
            if (row == n - 1)
                ++col;
            else
                ++row;
            row_inc = false;
        }

        // Print the next half
        // zig-zag pattern
        int MAX = Math.Max(m, n) - 1;
        for (int len, diag = MAX; diag > 0; --diag) {

            if (diag > mn)
                    len = mn;
            else
                len = diag;

            for (int i = 0; i < len; ++i) {
                    Console.Write(arr[row, col] + " ");

                if (i + 1 == len)
                    break;

                // Update row or col value
                // according to the last
                // increment
                if (row_inc) {
                        ++row;
                        --col;
                }
                else {
                    ++col;
                    --row;
                }
            }

            // Update the indexes of
            // row and col variable
            if (row == 0 || col == m - 1) {
                if (col == m - 1)
                    ++row;
                else
                    ++col;

                row_inc = true;
            }

            else if (col == 0 || row == n - 1) {
                if (row == n - 1)
                    ++col;
                else
                    ++row;

                row_inc = false;
            }
        }
    }

    // Driver code
    public static void Main()
    {
        int[, ] matrix = { { 1, 2, 3 },
                        { 4, 5, 6 },
                        { 7, 8, 9 } };
        zigZagMatrix(matrix, 3, 3);
    }
}

// This code is contributed by vt_m.

PHP

<?php
// PHP Program to print
// matrix in Zig-zag pattern
$C = 3;

// Utility function
// to print matrix
// in zig-zag form
function zigZagMatrix($arr,
                      $n, $m)
{
    $row = 0; $col = 0;

    // Boolean variable that
    // will true if we need
    // to increment 'row'
    // value otherwise false-
    // if increment 'col' value
    $row_inc = false;

    // Print matrix of lower
    // half zig-zag pattern
    $mn = min($m, $n);
    for ($len = 1;
         $len <= $mn; $len++)
    {
        for ($i = 0;
             $i < $len; $i++)
        {
            echo ($arr[$row][$col]." ");

            if ($i + 1 == $len)
                break;

            // If row_increment value
            // is true increment row
            // and decrement col else
            // decrement row and
            // increment col
            if ($row_inc)
            {
                $row++; $col--;
            }
            else
            {
                $row--; $col++;
            }
        }

        if ($len == $mn)
            break;

        // Update row or col
        // value according
        // to the last increment
        if ($row_inc)
        {
            ++$row; $row_inc = false;
        }
        else
        {
            ++$col; $row_inc = true;
        }
    }

    // Update the indexes of
    // row and col variable
    if ($row == 0)
    {
        if ($col == $m - 1)
            ++$row;
        else
            ++$col;
        $row_inc = 1;
    }
    else
    {
        if ($row == $n - 1)
            ++$col;
        else
            ++$row;
        $row_inc = 0;
    }

    // Print the next half
    // zig-zag pattern
    $MAX = max($m, $n) - 1;
    for ($len, $diag = $MAX;
         $diag > 0; --$diag)
    {
        if ($diag > $mn)
            $len = $mn;
        else
            $len = $diag;

        for ($i = 0;
             $i < $len; ++$i)
        {
            echo($arr[$row][$col] . " ");

            if ($i + 1 == $len)
                break;

            // Update row or col
            // value according to
            // the last increment
            if ($row_inc)
            {
                ++$row; --$col;
            }
            else
            {
                ++$col; --$row;
            }
        }

        // Update the indexes of
        // row and col variable
        if ($row == 0 ||
            $col == $m - 1)
        {
            if ($col == $m - 1)
                ++$row;
            else
                ++$col;

            $row_inc = true;
        }

        else if ($col == 0 ||
                 $row == $n - 1)
        {
            if ($row == $n - 1)
                ++$col;
            else
                ++$row;

            $row_inc = false;
        }
    }
}

// Driver code
$matrix = array(array(1, 2, 3),
                array(4, 5, 6),
                array(7, 8, 9));

zigZagMatrix($matrix, 3, 3);

// This code is contributed by
// Manish Shaw(manishshaw1)
?>

Javascript

// Javascript Program to print matrix in Zig-zag pattern
var n = 3, m = 3;
var a = [[ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]];
var zigZagMatrix=function(arr, n, m)
{
    var row = 0;
    var col = 0;

    // Variable that will be 1 if we
    // need to increment 'row' value and 0 otherwise
    // if we need to increment 'col' value
    var row_inc = 0;

    // print matrix of lower half zig-zag pattern
    var mn = Math.min(m, n);
    for (var len = 1; len <= mn; ++len) {
        for (var i = 0; i < len; ++i) {
            console.log(arr[row][col]);
            console.log(" ");

            if (i + 1 == len)
                break;
            // If row_increment value is true
            // increment row and decrement col
            // else decrement row and increment col
            if (row_inc)
                ++row, --col;
            else
                --row, ++col;
        }

        if (len == mn)
            break;

        // Update row or col value according
        // to the last increment
        if (row_inc)
            ++row, row_inc = false;
        else
            ++col, row_inc = true;
    }

    // Update the indexes of row and col variable
    if (row == 0) {
        if (col == m - 1)
            ++row;
        else
            ++col;
        row_inc = 1;
    }
    else {
        if (row == n - 1)
            ++col;
        else
            ++row;
        row_inc = 0;
    }

    // Print the next half zig-zag pattern
    var MAX = Math.max(m, n) - 1;
    for (var len, diag = MAX; diag > 0; --diag) {

        if (diag > mn)
            len = mn;
        else
            len = diag;

        for (var i = 0; i < len; ++i) {
            console.log(arr[row][col]);
            console.log(" ");
            if (i + 1 == len)
                break;

            // Update row or col value according
            // to the last increment
            if (row_inc)
                ++row, --col;
            else
                ++col, --row;
        }

        // Update the indexes of row and col variable
        if (row == 0 || col == m - 1) {
            if (col == m - 1)
                ++row;
            else
                ++col;

            row_inc = true;
        }

        else if (col == 0 || row == n - 1) {
            if (row == n - 1)
                ++col;
            else
                ++row;
            row_inc = false;
        }
    }
}
zigZagMatrix(a, 3, 3);

// This code is contributed by Sajal Aggarwal.

Output

1 2 4 7 5 3 6 8 9 

Time complexity: O(n*m)
Auxiliary space: O(1), since no extra space has been taken.