Tasks Details
easy
Minimize the value |(A[0] + ... + A[P-1]) - (A[P] + ... + A[N-1])|.
Task Score
100%
Correctness
100%
Performance
100%
A non-empty array A consisting of N integers is given. Array A represents numbers on a tape.
Any integer P, such that 0 < P < N, splits this tape into two non-empty parts: A[0], A[1], ..., A[P − 1] and A[P], A[P + 1], ..., A[N − 1].
The difference between the two parts is the value of: |(A[0] + A[1] + ... + A[P − 1]) − (A[P] + A[P + 1] + ... + A[N − 1])|
In other words, it is the absolute difference between the sum of the first part and the sum of the second part.
For example, consider array A such that:
A[0] = 3 A[1] = 1 A[2] = 2 A[3] = 4 A[4] = 3We can split this tape in four places:
- P = 1, difference = |3 − 10| = 7
- P = 2, difference = |4 − 9| = 5
- P = 3, difference = |6 − 7| = 1
- P = 4, difference = |10 − 3| = 7
Write a function:
object Solution { def solution(a: Array[Int]): Int }
that, given a non-empty array A of N integers, returns the minimal difference that can be achieved.
For example, given:
A[0] = 3 A[1] = 1 A[2] = 2 A[3] = 4 A[4] = 3the function should return 1, as explained above.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [2..100,000];
- each element of array A is an integer within the range [−1,000..1,000].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Scala
Time spent on task 11 minutes
Notes
not defined yet
Task timeline
Code: 04:41:44 UTC,
scala,
verify,
result: Failed
Analysis
Compile error
Solution.scala:10: error: @tailrec annotated method contains no recursive calls
def go(P: Int): Int = 2
^
one error found
Code: 04:42:38 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 = {
@scala.annotation.tailrec
def go(P: Int, currentMin: Int): Int = {
if (P >= A.length) currentMin
else go(P + 1, currentMin)
}
go(1, Int.MaxValue)
}
}
Analysis
expand all
Example tests
1.
2.257 s
WRONG ANSWER,
got 2147483647 expected 1
Code: 04:46:36 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentvalue = A(P - 1)
val newRightSide = rightSide - newRightSide
val leftSide = sum - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue)
}
}
Analysis
Compile error
Solution.scala:16: error: recursive value newRightSide needs type
val newRightSide = rightSide - newRightSide
^
Solution.scala:17: error: not found: value sum
val leftSide = sum - newRightSide
^
Solution.scala:23: error: not enough arguments for method go: (P: Int, currentMin: Int, rightSide: Int)Int.
Unspecified value parameter rightSide.
go(1, Int.MaxValue)
^
three errors found
Code: 04:47:03 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentvalue = A(P - 1)
val newRightSide = rightSide - newRightSide
val leftSide = sum - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue, total)
}
}
Analysis
Compile error
Solution.scala:16: error: recursive value newRightSide needs type
val newRightSide = rightSide - newRightSide
^
Solution.scala:17: error: not found: value sum
val leftSide = sum - newRightSide
^
two errors found
Code: 04:47:57 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentvalue = A(P - 1)
val newRightSide = rightSide - newRightSide
val leftSide = total - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue, total)
}
}
Analysis
Compile error
Solution.scala:16: error: recursive value newRightSide needs type
val newRightSide = rightSide - newRightSide
^
one error found
Code: 04:48:32 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentvalue = A(P - 1)
val newRightSide = rightSide - currentValue
val leftSide = total - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue, total)
}
}
Analysis
Compile error
Solution.scala:16: error: not found: value currentValue
val newRightSide = rightSide - currentValue
^
one error found
Code: 04:49:08 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentValue = A(P - 1)
val newRightSide = rightSide - currentValue
val leftSide = total - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue, total)
}
}
Analysis
Code: 04:50:04 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentValue = A(P - 1)
val newRightSide = rightSide - currentValue
val leftSide = total - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue, total)
}
}
Analysis
Code: 04:50:20 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 total = A.sum
@scala.annotation.tailrec
def go(P: Int, currentMin: Int, rightSide: Int): Int = {
if (P >= A.length) currentMin
else {
val currentValue = A(P - 1)
val newRightSide = rightSide - currentValue
val leftSide = total - newRightSide
val newMin = math.abs(leftSide - newRightSide) min currentMin
go(P + 1, newMin, newRightSide)
}
}
go(1, Int.MaxValue, total)
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N)
expand all
Correctness tests
1.
2.322 s
OK
2.
2.318 s
OK
1.
2.334 s
OK
1.
2.313 s
OK
1.
2.319 s
OK
1.
2.361 s
OK
1.
2.313 s
OK
expand all
Performance tests
1.
2.702 s
OK
1.
2.796 s
OK
1.
2.750 s
OK
2.
2.741 s
OK
1.
2.818 s
OK
2.
2.915 s
OK
1.
2.768 s
OK
1.
2.745 s
OK
2.
2.909 s
OK
3.
2.770 s
OK