Tasks Details
medium
1.
MaxCounters
Calculate the values of counters after applying all alternating operations: increase counter by 1; set value of all counters to current maximum.
Task Score
100%
Correctness
100%
Performance
100%
You are given N counters, initially set to 0, and you have two possible operations on them:
- increase(X) − counter X is increased by 1,
- max counter − all counters are set to the maximum value of any counter.
A non-empty array A of M integers is given. This array represents consecutive operations:
- if A[K] = X, such that 1 ≤ X ≤ N, then operation K is increase(X),
- if A[K] = N + 1 then operation K is max counter.
For example, given integer N = 5 and array A such that:
A[0] = 3 A[1] = 4 A[2] = 4 A[3] = 6 A[4] = 1 A[5] = 4 A[6] = 4the values of the counters after each consecutive operation will be:
(0, 0, 1, 0, 0) (0, 0, 1, 1, 0) (0, 0, 1, 2, 0) (2, 2, 2, 2, 2) (3, 2, 2, 2, 2) (3, 2, 2, 3, 2) (3, 2, 2, 4, 2)The goal is to calculate the value of every counter after all operations.
Write a function:
class Solution { public int[] solution(int N, int[] A); }
that, given an integer N and a non-empty array A consisting of M integers, returns a sequence of integers representing the values of the counters.
Result array should be returned as an array of integers.
For example, given:
A[0] = 3 A[1] = 4 A[2] = 4 A[3] = 6 A[4] = 1 A[5] = 4 A[6] = 4the function should return [3, 2, 2, 4, 2], as explained above.
Write an efficient algorithm for the following assumptions:
- N and M are integers within the range [1..100,000];
- each element of array A is an integer within the range [1..N + 1].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used C#
Time spent on task 5 minutes
Notes
not defined yet
Code: 14:39:11 UTC,
cs,
verify,
result: Failed
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N++;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne && maxCounterValue > 0)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
expand all
Example tests
1.
0.058 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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: 14:40:22 UTC,
cs,
verify,
result: Failed
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N++;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne && maxCounterValue > 0)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
expand all
Example tests
1.
0.060 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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: 14:41:11 UTC,
cs,
verify,
result: Failed
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution
{
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N++;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne && maxCounterValue > 0)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
expand all
Example tests
1.
0.058 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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: 14:41:51 UTC,
cs,
verify,
result: Failed
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution
{
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N++;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
expand all
Example tests
1.
0.058 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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.NullReferenceException: Object reference not set to an instance of an object at SolutionWrapper._codility_save_result (System.String _codility_filename) [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: 14:42:21 UTC,
cs,
verify,
result: Passed
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution
{
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N + 1;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
Code: 14:42:39 UTC,
cs,
verify,
result: Passed
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution
{
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N + 1;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne && maxCounterValue > 0)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
Code: 14:42:55 UTC,
cs,
verify,
result: Passed
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution
{
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N + 1;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne && maxCounterValue > 0)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}
Analysis
Code: 14:43:00 UTC,
cs,
final,
score:
100
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657
using System;
// you can also use other imports, for example:
// using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution
{
public int maxCounterValue;
public int[] Counters;
public void Increase(int position)
{
position = position - 1;
Counters[position]++;
if (Counters[position] > maxCounterValue)
maxCounterValue = Counters[position];
}
public void SetMaxCounter()
{
for (int i = 0; i < Counters.Length; i++)
{
Counters[i] = maxCounterValue;
}
}
public int[] solution(int N, int[] A)
{
if (N < 1 || N > 100000) return null;
if (A.Length < 1) return null;
int nlusOne = N + 1;
Counters = new int[N];
int x;
for (int i = 0; i < A.Length; i++)
{
x = A[i];
if (x > 0 && x <= N)
{
Increase(x);
}
if (x == nlusOne && maxCounterValue > 0)
SetMaxCounter();
if (x > nlusOne)
return null;
}
return Counters;
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N + M)
expand all
Performance tests
1.
0.069 s
OK
1.
0.065 s
OK
1.
0.235 s
OK
1.
0.419 s
OK
1.
0.120 s
OK
2.
0.105 s
OK