如何在ZigZag路径中遍历和打印2D数组

Question

Suppose I have an array

A[][] = {{ 1, 2, 3, 4},
         { 5, 6, 7, 8},
         { 9,10,11,12}};

And I want to print a wave so that the output comes out like this

{1,5,9,10,6,2,3,7,11,12,8,4}

How can I do this??

here is my code but it is giving me ArrayIndexOutOfBound

public class Wave1 {

public static void main(String[] args) {
    // TODO Auto-generated method stub
    int [][] a={{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16},{17,18,19,20}} ;
    System.out.println("Row "+a.length);
    for(int i=0;i<a.length;i++){
        System.out.println("Column "+i+"th "+a[i].length);
    }
    for(int i=0;i<a.length;i++){
        for(int j=0;j<a[i].length;j++){
            System.out.print(a[i][j]+" ");
        }
    }
    System.out.println();
    for(int i=0;i<a.length+1;i++){
        if(i%2==0){
        for(int j=0;j<a.length;j++){
            System.out.print(a[j][i]+" ");
        }
    }
    else{
        for(int j=a.length-1;j>=0;j--){
            System.out.print(a[j][i]+" ");

        }
    }
}

Thanks in advance

Answer 1

It seems what you want is to print each column of the matrix, where the even indexed columns are printed in ascending order and the odd indexed columns are printed in descending order.

for (int col = 0; col < a[0].length; col++) {
    if (col % 2 == 0) {
        for (int row = 0; row < a.length; row++)
            System.out.print(a[row][col] + " ");
        System.out.println();
    } else {
        for (int row = a.length - 1; row >= 0; row--)
            System.out.print(a[row][col] + " ");
        System.out.println();
    }
}

Output :

1 5 9 13 17 
18 14 10 6 2 
3 7 11 15 19 
20 16 12 8 4 

Answer 2

You can do it easily by taking two for loops, one for forward scanning and another for backward scanning.

Here is the code snippet:

public static void main (String[] args)
{
    int [][] a={{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16},{17,18,19,20}};

    for(int k = 0;k < 4;k++) {
        for(int i = 0;i < a.length;i++) {
            System.out.print(a[i][k] + " ");
        }

        k++;
        for(int i = a.length - 1;i >=0 ;i--) {
            System.out.print(a[i][k] + " ");
        }
    }
}

Output:

1 5 9 13 17 18 14 10 6 2 3 7 11 15 19 20 16 12 8 4 

Answer 3

That's like traversing an array similiar to traversing a tree in zigzag traversal, but in this case we do not need stacks just modular arithmetich will be enough, here is your solution;

Method #1 - dummyPrint

private static void dummyPrint(int[][] array) {
    System.out.print("Dummy Print: ");

    for(int j = 0; j < array[0].length; j++) {
        if(j%2 == 0) {
            for(int i = 0; i < array.length; i++)
                System.out.printf("%2d ", array[i][j]);
        } else {
            for(int i = array.length-1; i >= 0; i--)
                System.out.printf("%2d ", array[i][j]);
        }
    }

    System.out.println();
}

Method #2 - prettyPrint

private static void prettyPrint(int[][] array) {
    System.out.println("Pretty Print;");
    System.out.println("*************");
    for(int j = 0; j < array[0].length; j++) {
        if(j%2 == 0) {
            for(int i = 0; i < array.length; i++)
                System.out.printf("%2d ", array[i][j]);
        } else {
            for(int i = array.length-1; i >= 0; i--)
                System.out.printf("%2d ", array[i][j]);
        }


        System.out.println();
    }
}

Demonstration Code

public class ArrayDemo {

    public static void main(String[] args) {
        int [][] array = {{1,2,3,4},{5,6,7,8},{9,10,11,12}};

        dummyPrint(array);

        System.out.println();

        prettyPrint(array);
    }

    private static void dummyPrint(int[][] array) {
        System.out.print("Dummy Print: ");

        for(int j = 0; j < array[0].length; j++) {
            if(j%2 == 0) {
                for(int i = 0; i < array.length; i++)
                    System.out.printf("%2d ", array[i][j]);
            } else {
                for(int i = array.length-1; i >= 0; i--)
                    System.out.printf("%2d ", array[i][j]);
            }
        }

        System.out.println();
    }

    private static void prettyPrint(int[][] array) {
        System.out.println("Pretty Print;");
        System.out.println("*************");
        for(int j = 0; j < array[0].length; j++) {
            if(j%2 == 0) {
                for(int i = 0; i < array.length; i++)
                    System.out.printf("%2d ", array[i][j]);
            } else {
                for(int i = array.length-1; i >= 0; i--)
                    System.out.printf("%2d ", array[i][j]);
            }


            System.out.println();
        }
    }
}

The Output

Dummy Print:  1  5  9 10  6  2  3  7 11 12  8  4 

Pretty Print;
*************
 1  5  9 
10  6  2 
 3  7 11 
12  8  4 

Answer 4

There is a discrepancy with the code you print and the desired output. In your code, there is a line that prints "row" and another that prints "column".

This code

public class Wave1 {   
  public static void main(String[] args) {
    int [][] a={{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16},{17,18,19,20}} ;
    String separator="";
    System.out.print("{");
    for (int[] row: a) {
      for (int cell: row) {
        System.out.print(separator+cell);
        separator=",";
      }
    }
    System.out.println("}");
  }
}

prints

{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20} 

I was not able to figure out the order in which the numbers should be printed. I assumed it did not matter.

Answer 5

public class Wave1 {

    public static void main(String args[])
    {
        int [][] wave={{1,2,3,4},{5,6,7,8},{8,9,10,11},{12,13,14,15}};
        for(int i=0;i<wave.length;i++){
            if(i%2==0){
            for(int j=0;j<wave[0].length;j++){
                System.out.print(wave[i][j]+" ");
                }
            System.out.println();
            }
            else{
                for(int j=wave[0].length-1;j>=0;j--){
                    System.out.print(wave[i][j]+" ");
                }
                System.out.println();
            }
        }
    }
}

Answer 6

public static void wave(int[][]input)
    {
        int row=0;
        int col=0;
        int steps=1;
        System.out.print(input[0][0]+" ");
        while(steps<=input.length*(input[0].length)-1)
        {
            if(col%2==1)
            {
                row--;

            }
            else
            {
                row++;

            }
            if(row<0)
            {
                row++;
                if(col%2==1)
                {
                    col++;
                }
            }
            if(row>input.length-1)
            {
                row--;
                if(col%2==0)
                {
                    col++;
                }

            }
            System.out.print(input[row][col]+" ");
            steps++;
        }

    }

Answer 7

Check this one: Use this function it will take 2D Array as its input and would print a zigzag Path

 public static void wavePrint(int input[][]){

   int count = 1;
   int rows = input.length;
   int cols = input[0].length;

   for(int i = 0; i < cols; i++){
       if(count % 2 != 0){           //odd column
           int sine_e = 0;
           while(sine_e < rows){
               System.out.print(input[sine_e][i]+" ");
               sine_e++;
           }
           count++;
       }else{
           int sine_e = rows - 1;          //even column
           while(sine_e >= 0){
               System.out.print(input[sine_e][i]+" ");
               sine_e--;
            }
            count++;
       }
   }//end of for loop
}