Improving Time Efficiency on two custom List in KOTLIN-CodePudding

There are two lists:

val listA:List<Amodel> 
val listB:List<Int>


data class Amodel(val id:Int,var isUsed:Boolean=false)

Need to update listA isUsed =true based on the int id of the listB

What I'm doing now:

listB.foreach(){
//here i'm updating but it's taking too much time w.r.t time efficiency.
}

any GOOD solution.

Note list size is 500k for simulation

CodePudding user response：

This might be slightly faster when the lists are huge:

val lookup = listB.associateWith { true }
listA.forEach { it.isUsed = lookup[it.id] ?: false }

Possibly this is even faster, I'm not sure. Because it then only sets isUsed in the case it needs to be true:

val lookup = listB.associateWith { true }
listA.forEach { lookup[it.id]?.run { it.isUsed = true } }

CodePudding user response：

data class Amodel(val id: Int, var isUsed: Boolean = false)

val listA: List<Amodel> = listOf(
  Amodel(1),
  Amodel(2),
  Amodel(3),
  Amodel(4),
  Amodel(5)
)
val listB: List<Int> = listOf(2, 4, 5)

listA.forEach { if (it.id in listB) it.isUsed = true }

// Alternative to set all items, not only from false to true:
listA.forEach { it.isUsed = it.id in listB }

println(listA)

Output:

[
  Amodel(id=1, isUsed=false),
  Amodel(id=2, isUsed=true), 
  Amodel(id=3, isUsed=false), 
  Amodel(id=4, isUsed=true), 
  Amodel(id=5, isUsed=true)
]