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How to Reverse keys and values in Scala Map

  • Last Updated : 13 Aug, 2019

In Scala, Map is same as dictionary which holds key:value pairs. In this article, we will learn how to reverse the keys and values in given Map in Scala. After reversing the pairs, keys will become values and values will become keys. We can reverse the keys and values of a map with a Scala for-comprehension. Keys should be unique for reverse these values otherwise we can lose some content.
Syntax:

val reverseMap = for ((k,v) <- map) yield (v, k)

Below is the example to reverse keys and values in Scala Map.

Example #1:




// Scala program to reverse keys and values
  
// Creating object 
object GfG 
  
    // Main method 
    def main(args:Array[String]) 
    
      
        // Creating a map 
        val m1 = Map(3 -> "geeks", 4 -> "for", 2 -> "cs"
          
        // reversing key:value pairs 
        val reverse = for ((k, v) <- m1) yield (v, k)
  
        // Displays output 
        println(reverse) 
      
    

Output:

Map(geeks -> 3, for -> 4, cs -> 2)

Example #2:




// Scala program to reverse keys and values
  
// Creating object 
object GfG 
  
    // Main method 
    def main(args:Array[String]) 
    
      
        // Creating a map 
        val mapIm = Map("Ajay" -> 30
                        "Bhavesh" -> 20
                        "Charlie" -> 50
          
        // Applying keySet method 
        val reverse = for ((k, v) <- mapIm) yield (v, k)
  
        // Displays output 
        println(reverse) 
      
    

Output:

Map(30 -> Ajay, 20 -> Bhavesh, 50 -> Charlie)



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