Question

Scala: Write and test a Program as elegantly as possible

Given a piece of text, create a histogram of letter pairs (order from high to low). For instance, for the text, “this is a good thing”,

the letter pairs are: th, hi, is, is, go, oo, od, th, hi, in, and ng. (ignore a) The histogram will be:
th: 2, is: 2, hi: 2 go: 1, oo: 1, od: 1, in: 1, ng: 1

Sample Input/Output:

Enter text: this is a good thing
Histogram: th: 2, is: 2, hi: 2 go: 1, oo: 1, od: 1, in: 1, ng: 1

Enter text: coooooool
Histogram: oo: 6, co: 1, ol: 1

Answer 1

Complete scala program with description in comments:

object Histogram {

def main(args: Array[String]) {
  
//take user input
println("Enter text:")
var input = scala.io.StdIn.readLine()
  
// length of the input string
var length = input.length()
var str = ""
  
// create an object of mutable LinkedHashMap
// key is string type, value is integer type for mainitaining count
val histogram = scala.collection.mutable.LinkedHashMap[String, Int]()
  
var index = 0
  
// traverse till second last character in the input string
// why second last: because we are creating histogram of pairs.
// last pair would be second last character and last character
for(index <- 0 to (length - 2))
{
// check if current character or next character not a white space
// this check ignores whitespaces and single letter
if( !(input(index) == ' ' || input(index+1) == ' '))
{
// prepare key by appending 2 characters
str = "" + input(index) + input(index+1)
  
// check if key already exists
// if exist just increment the value by 1
if(histogram.contains(str))
{
histogram(str) = histogram(str) + 1
}
// if key doesn't exist, insert it in map with count value one
else
{
histogram(str) = 1
}
}
}
  
print("Histogram:")
// print the key value pair using map iterator foreach
histogram.keys.foreach{ key => print( " " + key + ": " + histogram(key) + ",")}
}

}

Sample run 1:

Enter text:
this is a good thing
th: 2, hi: 2, is: 2, go: 1, oo: 1, od: 1, in: 1, ng: 1,

Sample run 2:

Enter text:
coooooool
co: 1, oo: 5, oo: 1, oo: 1, ol: 1,