Tasks Details
medium
Find the minimal average of any slice containing at least two elements.
Task Score
50%
Correctness
40%
Performance
60%
A non-empty array A consisting of N integers is given. A pair of integers (P, Q), such that 0 ≤ P < Q < N, is called a slice of array A (notice that the slice contains at least two elements). The average of a slice (P, Q) is the sum of A[P] + A[P + 1] + ... + A[Q] divided by the length of the slice. To be precise, the average equals (A[P] + A[P + 1] + ... + A[Q]) / (Q − P + 1).
For example, array A such that:
A[0] = 4 A[1] = 2 A[2] = 2 A[3] = 5 A[4] = 1 A[5] = 5 A[6] = 8contains the following example slices:
- slice (1, 2), whose average is (2 + 2) / 2 = 2;
- slice (3, 4), whose average is (5 + 1) / 2 = 3;
- slice (1, 4), whose average is (2 + 2 + 5 + 1) / 4 = 2.5.
The goal is to find the starting position of a slice whose average is minimal.
Write a function:
class Solution { public int solution(int[] A); }
that, given a non-empty array A consisting of N integers, returns the starting position of the slice with the minimal average. If there is more than one slice with a minimal average, you should return the smallest starting position of such a slice.
For example, given array A such that:
A[0] = 4 A[1] = 2 A[2] = 2 A[3] = 5 A[4] = 1 A[5] = 5 A[6] = 8the 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 [−10,000..10,000].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used C#
Time spent on task 29 minutes
Notes
not defined yet
Code: 07:44:01 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
int smallestNum;
int index;
for (int i = 0; i < (A.length - 1); i++) {
int tmp = (A[i] + A[i + 1]) / 2
if(tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
return index;
}
}
}
Analysis
Compile error
Compilation failed: 3 error(s), 0 warnings Solution.cs(15,12): error CS1525: Unexpected symbol `if' Solution.cs(15,32): error CS1525: Unexpected symbol `)' Solution.cs(26,0): error CS1525: Unexpected symbol `}'
Code: 07:44:21 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
int smallestNum;
int index;
for (int i = 0; i < (A.length - 1); i++) {
int tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
return index;
}
}
}
Analysis
Compile error
Compilation failed: 1 error(s), 0 warnings Solution.cs(13,32): error CS1061: Type `int[]' does not contain a definition for `length' and no extension method `length' of type `int[]' could be found. Are you missing an assembly reference? /opt/lang/mono/lib/mono/4.5/mscorlib.dll (Location of the symbol related to previous error)
Code: 07:45:06 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum;
int index;
for (int i = 0; i < (A.length - 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
return index;
}
}
}
Analysis
Compile error
Compilation failed: 1 error(s), 0 warnings Solution.cs(13,32): error CS1061: Type `int[]' does not contain a definition for `length' and no extension method `length' of type `int[]' could be found. Are you missing an assembly reference? /opt/lang/mono/lib/mono/4.5/mscorlib.dll (Location of the symbol related to previous error)
Code: 07:46:03 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum;
int index;
for (int i = 0; i < (A.Length - 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
return index;
}
}
}
Analysis
Compile error
Compilation failed: 3 error(s), 1 warnings Solution.cs(9,16): error CS0161: `Solution.solution(int[])': not all code paths return a value Solution.cs(15,23): error CS0165: Use of unassigned local variable `smallestNum' Solution.cs(19,20): error CS0165: Use of unassigned local variable `index' Solution.cs(13,45): warning CS0162: Unreachable code detected
Code: 07:46:40 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length - 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
return index;
}
}
}
Analysis
Compile error
Compilation failed: 1 error(s), 1 warnings Solution.cs(9,16): error CS0161: `Solution.solution(int[])': not all code paths return a value Solution.cs(13,45): warning CS0162: Unreachable code detected
Code: 07:47:03 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length + 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
return index;
}
}
}
Analysis
Compile error
Compilation failed: 1 error(s), 1 warnings Solution.cs(9,16): error CS0161: `Solution.solution(int[])': not all code paths return a value Solution.cs(13,45): warning CS0162: Unreachable code detected
Code: 07:47:43 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length + 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
}
return index;
}
}
Analysis
expand all
Example tests
1.
0.048 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Unhandled Exception: System.IndexOutOfRangeException: Array index is out of range. at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0 [ERROR] FATAL UNHANDLED EXCEPTION: System.IndexOutOfRangeException: Array index is out of range. at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0
Code: 07:48:53 UTC,
cs,
verify,
result: Failed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length + 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
}
return index;
}
}
Analysis
expand all
Example tests
1.
0.049 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Unhandled Exception: System.IndexOutOfRangeException: Array index is out of range. at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0 [ERROR] FATAL UNHANDLED EXCEPTION: System.IndexOutOfRangeException: Array index is out of range. at Solution.solution (System.Int32[] A) [0x00000] in <filename unknown>:0 at SolutionWrapper.run (System.String input, System.String output) [0x00000] in <filename unknown>:0 at SolutionWrapper.Main (System.String[] args) [0x00000] in <filename unknown>:0
Code: 07:49:15 UTC,
cs,
verify,
result: Passed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length - 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
}
return index;
}
}
Analysis
Code: 07:49:49 UTC,
cs,
verify,
result: Passed
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length - 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
}
return index;
}
}
Analysis
Code: 07:49:52 UTC,
cs,
final,
score:
50
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can write to stdout for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
float smallestNum = A[0];
int index = 0;
for (int i = 0; i < (A.Length - 1); i++) {
float tmp = (A[i] + A[i + 1]) / 2;
if (tmp < smallestNum) {
smallestNum = tmp;
index = i;
}
}
return index;
}
}Analysis summary
The following issues have been detected: wrong answers.
For example, for the input [-3, -5, -8, -4, -10] the solution returned a wrong answer (got 3 expected 2).
Analysis
expand all
Correctness tests
1.
0.053 s
OK
2.
0.052 s
OK
3.
0.051 s
OK
4.
0.050 s
OK
1.
0.050 s
OK
2.
0.051 s
WRONG ANSWER,
got 2 expected 5
1.
0.053 s
WRONG ANSWER,
got 3 expected 2
1.
0.052 s
OK
medium_range
increasing, decreasing (legth = ~100) and small functional
increasing, decreasing (legth = ~100) and small functional
✘
WRONG ANSWER
got 0 expected 3
got 0 expected 3
1.
0.051 s
OK
2.
0.052 s
OK
3.
0.051 s
WRONG ANSWER,
got 0 expected 3
expand all
Performance tests
1.
0.055 s
OK
1.
0.075 s
OK
2.
0.066 s
WRONG ANSWER,
got 0 expected 40002
1.
0.085 s
OK
1.
0.082 s
OK
2.
0.086 s
OK
3.
0.084 s
OK
1.
0.074 s
WRONG ANSWER,
got 2 expected 3
2.
0.069 s
WRONG ANSWER,
got 1 expected 4