Tasks Details
easy
Find the missing element in a given permutation.
Task Score
100%
Correctness
100%
Performance
100%
An array A consisting of N different integers is given. The array contains integers in the range [1..(N + 1)], which means that exactly one element is missing.
Your goal is to find that missing element.
Write a function:
object Solution { def solution(a: Array[Int]): Int }
that, given an array A, returns the value of the missing element.
For example, given array A such that:
A[0] = 2 A[1] = 3 A[2] = 1 A[3] = 5the function should return 4, as it is the missing element.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [0..100,000];
- the elements of A are all distinct;
- each element of array A is an integer within the range [1..(N + 1)].
Copyright 2009–2024 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Scala
Time spent on task 2 minutes
Notes
not defined yet
Task timeline
Code: 00:20:49 UTC,
scala,
verify,
result: Failed
import scala.collection.JavaConversions._
// you can use println for debugging purposes, e.g.
// println("this is a debug message")
object Solution {
def solution(A: Array[Int]): Int = {
val N = (A.length + 1).toLong
val expectedSum = (N) * (N + 1) / 2
expectedSum - A.view.map(_.toLong).sum
}
}
Analysis
Compile error
Solution.scala:10: error: type mismatch;
found : Long
required: Int
expectedSum - A.view.map(_.toLong).sum
^
one error found
Code: 00:21:09 UTC,
scala,
verify,
result: Passed
import scala.collection.JavaConversions._
// you can use println for debugging purposes, e.g.
// println("this is a debug message")
object Solution {
def solution(A: Array[Int]): Int = {
val N = (A.length + 1).toLong
val expectedSum = (N) * (N + 1) / 2
val actualSum = A.view.map(_.toLong).sum
(expectedSum - actualSum).toInt
}
}
Analysis
Code: 00:21:37 UTC,
scala,
verify,
result: Passed
import scala.collection.JavaConversions._
// you can use println for debugging purposes, e.g.
// println("this is a debug message")
object Solution {
def solution(A: Array[Int]): Int = {
val N = (A.length + 1).toLong
val expectedSum = (N) * (N + 1) / 2
val actualSum = A.view.map(_.toLong).sum
(expectedSum - actualSum).toInt
}
}
Analysis
Code: 00:21:52 UTC,
scala,
final,
score:
100
import scala.collection.JavaConversions._
// you can use println for debugging purposes, e.g.
// println("this is a debug message")
object Solution {
def solution(A: Array[Int]): Int = {
val N = (A.length + 1).toLong
val expectedSum = (N) * (N + 1) / 2
val actualSum = A.view.map(_.toLong).sum
(expectedSum - actualSum).toInt
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Correctness tests
1.
2.438 s
OK
2.
2.446 s
OK
1.
2.446 s
OK
2.
2.424 s
OK
1.
2.424 s
OK
2.
2.435 s
OK
1.
2.448 s
OK
2.
2.463 s
OK
3.
2.437 s
OK
1.
2.429 s
OK
expand all
Performance tests
1.
2.743 s
OK
1.
2.777 s
OK
1.
2.925 s
OK
2.
2.860 s
OK
3.
3.089 s
OK
1.
2.935 s
OK
1.
2.901 s
OK