How to draw Pyramid Shapes using Kotlin

Varanasi Software Junction December 26, 2020

 Consider the following figure

O
OO
OOO
OOOO
This will be drawn using nested loops so let us make a chart

i        No of Os

1            1
2            2
3            3
4            4

This means we run a loop from 1 to 4 and run a nested loop from 1 to i inside the first loop

fun main(args : Array<String>)
{
var n:Int =4
var row:Int
 for( row in 1..n)
{
var col:Int
for(col in 1..row)
print("O")
 println()
}
}

Varanasi Software Junction: Kotlin Pyramid

Consider this figure now
    
         O
      OO
   OOO
OOOO
This figure will require printing spaces on the left side before the Os. Let us make a chart again

Row        Space        Os
1                3                1
2                2                2
3                1                3
4                0                4

This will require an outer loop from 1 to 4 which will have 2 inner loops, one for the space and the other for Os
Space will be n-row, while Os will be row

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        for(col in 1..row)
            print("O")
        println()

    }
}

Varanasi Software Junction: Kotlin Shape

To vertically reverse a shape simply reverse the row loop.

 

fun main(args : Array<String>)

{

    var n:Int =4

    var row:Int

    for( row in n downTo 1)

    {

        var space:Int

        for(space in 1..n-row)

            print(" ")

        var col:Int

        for(col in 1..row)

            print("O")

        println()


    }

}

Varanasi Software Junction: Kotlin Shape

Next shape

      O
   OOO
OOOOO

Row        Space        Os
1                3                1
2                2                3
3                1                5
 
The number of Os is an odd number series. This can be generated by running a loop from 1 to 2*row -1

fun main(args : Array<String>)
{
var n:Int =3
var row:Int
 for( row in 1..n)
 {
var space:Int
 for(space in 1..n-row)
print(" ")
var col:Int
for(col in 1..2*row-1)
print("O")
 println()
}
}

 


Varanasi Software Junction: Kotlin Shape

Next figure,
1
1 2 
1 2 3
1 2 3 4 
First of all let us get the figure right
Row        Col
1                1
1                2
1                3
1                4
The shape can be drawn by the following program

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        var col:Int
        for(col in 1..row)
            print("O")
        println()

    }
}

Varanasi Software Junction: Kotlin Shape

Now print the col value instead of O

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        var col:Int
        for(col in 1..row)
            print(col)
        println()

    }
}


How about printing the following figure.
A
AB
ABC
ABCD

Its the same figure as before with the added conversion to Characters.

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        var col:Int
        for(col in 1..row) {
            var ch:Char
            ch=('A'.toInt() + col-1).toChar()
            print(ch)
        }
        println()

    }
}


Varanasi Software Junction: Kotlin Shape


How about this figure?

         1
      1 2 1
   1 2 3 2 1
1 2 3 4 3 2 1

This figure has the exact shape of the pyramid drawn above and is based on the odd number sequence. 
Here is the code for that 
fun main(args : Array<String>)
{
var n:Int =3
var row:Int
 for( row in 1..n)
 {
var space:Int
 for(space in 1..n-row)
print(" ")
var col:Int
for(col in 1..2*row-1)
print("O")
 println()
}
}
Varanasi Software Junction:Kotlin Shape

Now, we will break up the 2*row-1 into row + row-1

fun main(args : Array<String>)
{
    var n:Int =3
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        for(col in 1..row)
            print("O")
        for(col in 1..row-1)
            print("O")
        println()
    }
}

The output will be the same. Now print col instead of "O" in the loops.
fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        for(col in 1..row)
            print(col)
        for(col in 1..row-1)
            print(col)
        println()
    }
}



Reverse the second loop now and we are done.

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        for(col in 1..row)
            print(col)
        for(col in row-1 downTo 1)
            print(col)
        println()
    }
}

Varanasi Software Junction:Kotlin Shape

What if we require alphabets?

         A
      ABA
   ABCBA
ABCDCBA


fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
}


Varanasi Software Junction:Kotlin Shape


Let us try this shape now.
      A
   ABA
ABCBA
   ABA
     A

We can break down this figure into 2 parts
      A
   ABA
ABCBA

and
ABA
  A

Reversing a figure is done via reversing the top loop. So, let us do a bit of copy paste and create 2 loops first.
fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    //First loop begins
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
//First loop ends

    //Second loop begins
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
    //Second loop ends



}


Varanasi Software Junction:Kotlin Shape


Reverse the second loop now.

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    //First loop begins
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
//First loop ends

    //Second loop begins
    for( row in n downTo 1)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
    //Second loop ends



}

Varanasi Software Junction:Kotlin Shape


The middle line is being repeated twice. Run the first loop upto n-1 or let the second one begin from n-1.

fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    //First loop begins
    for( row in 1..n)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
//First loop ends

    //Second loop begins
    for( row in n-1 downTo 1)
    {
        var space:Int
        for(space in 1..n-row)
            print(" ")
        var col:Int
        var ch:Char
        for(col in 1..row) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        for(col in row-1 downTo 1) {
            ch = ('A'.toInt() + col - 1).toChar()
            print(ch)
        }
        println()
    }
    //Second loop ends



}


Varanasi Software Junction:Kotlin Shape





How to draw an outline figure?

OOOOO
O        O
O        O
O        O
OOOOO

First activity should be to draw a complete shape
OOOOO
OOOOO
OOOOO
OOOOO
OOOOO
fun main(args : Array<String>)
{
    var n:Int =4
    var row:Int
    
    for( row in 1..n)
    {

        for(col in 1..n) {
            print("O")
        }

        println()
    }

    }



Varanasi Software Junction: Kotlin Shape








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