Print a matrix in alternate manner (left to right then right to left) - GeeksforGeeks

22 Apr, 2021
Given a 2D array, the task is to print the 2D in alternate manner (First row from left to right, then from right to left, and so on). Examples:  
Input : arr[][2] = {{1, 2}
                    {2, 3}}; 
Output : 1  2  3  2 
 
Input :arr[][3] = { { 7 , 2 , 3 },
                    { 2 , 3 , 4 },
                    { 5 , 6 ,  1 }}; 
Output : 7  2   3  4  3  2  5  6  1
 
The solution of this problem is that run two loops and and print row in left to right and right to left manners. We maintain a flag to see if current row should be printed from left to right or right to left. We toggle the flag after every iteration. 
C++
Java
Python 3
C#
PHP
Javascript
// C++ program to print matrix in alternate manner#include<bits/stdc++.h>using namespace std;#define R 3#define C 3 // Function for print matrix in alternate mannervoid convert(int arr[R][C]){    bool leftToRight = true;    for (int i=0; i<R; i++)    {        if (leftToRight)        {            for (int j=0; j<C; j++)                printf("%d ", arr[i][j]);        }        else        {            for (int j=C-1; j>=0; j--)                printf("%d ",arr[i][j]);        }         leftToRight = !leftToRight;    }} // Driver codeint main(){    int arr[][C] =    {        { 1 , 2 , 3 },        { 3 , 2 , 1 },        { 4 , 5 , 6 },    };     convert(arr);    return 0;}
//Java program to print matrix in alternate mannerclass GFG {     static final int R = 3;    static final int C = 3; // Function for print matrix in alternate manner    static void convert(int arr[][]) {        boolean leftToRight = true;        for (int i = 0; i < R; i++) {            if (leftToRight) {                for (int j = 0; j < C; j++) {                    System.out.printf("%d ", arr[i][j]);                }            } else {                for (int j = C - 1; j >= 0; j--) {                    System.out.printf("%d ", arr[i][j]);                }            }             leftToRight = !leftToRight;        }    } // Driver code    static public void main(String[] args) {        int arr[][]                = {                    {1, 2, 3},                    {3, 2, 1},                    {4, 5, 6},};         convert(arr);    }} // This code is contributed by Rajput-Ji
# Python 3 program to print matrix# in alternate mannerR = 3C = 3 # Function for print matrix# in alternate mannerdef convert(arr):     leftToRight = True    for i in range(R):        if (leftToRight):            for j in range(C):                print(arr[i][j], end = " ")             else:            for j in range(C - 1, -1, -1):                print(arr[i][j], end = " ")         leftToRight = not leftToRight # Driver codeif __name__ == "__main__":    arr =[[ 1 , 2 , 3 ],          [ 3 , 2 , 1 ],          [ 4 , 5 , 6 ]]     convert(arr) # This code is contributed# by ChitraNayal
     //C# program to print matrix in alternate mannerusing System;public class GFG {      static readonly int R = 3;    static readonly int C = 3;  // Function for print matrix in alternate manner    static void convert(int [,]arr) {        bool leftToRight = true;        for (int i = 0; i < R; i++) {            if (leftToRight) {                for (int j = 0; j < C; j++) {                    Console.Write(arr[i,j]+" ");                }            } else {                for (int j = C - 1; j >= 0; j--) {                    Console.Write(arr[i,j]+" ");                }            }              leftToRight = !leftToRight;        }    }  // Driver code    static public void Main() {        int [,]arr                = {                    {1, 2, 3},                    {3, 2, 1},                    {4, 5, 6},};          convert(arr);    }}  // This code is contributed by Rajput-Ji
<?php// PHP program to print matrix// in alternate manner$R = 3;$C = 3; // Function for print matrix// in alternate mannerfunction convert($arr){    global $R;    global $C;    $leftToRight = true;    for ($i = 0; $i < $R; $i++)    {        if ($leftToRight)        {            for ($j = 0; $j < $C; $j++)                echo $arr[$i][$j], " ";        }        else        {            for ($j = $C - 1; $j >= 0; $j--)                echo $arr[$i][$j], " ";        }         $leftToRight = !$leftToRight;    }} // Driver code$arr = array(array(1 , 2 , 3 ),             array(3 , 2 , 1 ),             array(4 , 5 , 6 )); convert($arr); // This code is contributed by ajit?>
<script>// Javascript program to print matrix in alternate manner    let R = 3;    let C = 3;         // Function for print matrix in alternate manner    function convert(arr)    {        let leftToRight = true;        for (let i = 0; i < R; i++) {            if (leftToRight) {                for (let j = 0; j < C; j++) {                    document.write(arr[i][j]+" ");                }            } else {                for (let j = C - 1; j >= 0; j--) {                    document.write( arr[i][j]+" ");                }            }               leftToRight = !leftToRight;        }    }         // Driver code    let arr =[[ 1 , 2 , 3 ],          [ 3 , 2 , 1 ],          [ 4 , 5 , 6 ]]    convert(arr)         // This code is contributed by avanitrachhadiya2155</script>
Output:  
1 2 3 1 2 3 4 5 6
Time Complexity : O(R*C) Space Complexity : O(1)This article is contributed by DANISH_RAZA. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. 
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