Tasks Details
medium
Find the smallest positive integer that does not occur in a given sequence.
Task Score
88%
Correctness
100%
Performance
75%
This is a demo task.
Write a function:
class Solution { public int solution(int[] A); }
that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.
For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.
Given A = [1, 2, 3], the function should return 4.
Given A = [−1, −3], the function should return 1.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [1..100,000];
- each element of array A is an integer within the range [−1,000,000..1,000,000].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Java 21
Time spent on task 26 minutes
Notes
not defined yet
Code: 11:25:34 UTC,
java,
verify,
result: Failed
Analysis
Compile error
Solution.java:7: error: cannot find symbol
A = A.sort(A);
^
symbol: method sort(int[])
location: variable A of type int[]
1 error
Code: 11:26:00 UTC,
java,
verify,
result: Failed
Analysis
Compile error
Solution.java:7: error: incompatible types: void cannot be converted to int[]
A = Arrays.sort(A);
^
1 error
Code: 11:27:00 UTC,
java,
verify,
result: Failed
Analysis
expand all
Example tests
1.
0.909 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:12) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)
expand all
User tests
1.
0.902 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -2 at Solution.solution(Solution.java:12) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)
1.
0.949 s
OK
function result: 1
function result: 1
1.
0.969 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:12) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)
1.
0.902 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -4 at Solution.solution(Solution.java:12) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)
User test case 1:
[1, -1]
User test case 2:
[0, -2]
User test case 3:
[1, 2, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:28:51 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
class Solution
{
public int solution(int[] A)
{
Arrays.sort(A);
int next = 1;
System.out.println(Arrays.binarySearch(A, 0));
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.353 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
-1
expand all
User tests
1.
1.350 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -2 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
-2
1.
1.341 s
OK
function result: 1
function result: 1
stdout:
1
1.
1.351 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
-1
1.
1.347 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -4 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
-4
User test case 1:
[1, -1]
User test case 2:
[0, -2]
User test case 3:
[1, 2, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:29:51 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
class Solution
{
public int solution(int[] A)
{
Arrays.sort(A);
int next = 1;
System.out.println(Arrays.toString(A));
System.out.println(Arrays.binarySearch(A, 0));
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.437 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:15) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1, 1, 2, 3, 4, 6] -1
expand all
User tests
1.
1.438 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -2 at Solution.solution(Solution.java:15) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[-1, 1] -2
1.
1.450 s
OK
function result: 1
function result: 1
stdout:
[-2, 0] 1
1.
1.428 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:15) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1, 2, 4] -1
1.
1.439 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -4 at Solution.solution(Solution.java:15) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[-5, -3, -2, 4] -4
User test case 1:
[1, -1]
User test case 2:
[0, -2]
User test case 3:
[1, 2, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:33:26 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
System.out.println( Arrays.(a) );
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
Compile error
Solution.java:7: error: illegal start of expression
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
^
Solution.java:7: error: ';' expected
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
^
Solution.java:7: error: illegal start of expression
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
^
Solution.java:7: error: ';' expected
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
^
Solution.java:7: error: illegal start of expression
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
^
Solution.java:7: error: ';' expected
int[] a = IntStream.of(A).distinct().filter( s -> return s > 0 ).toArray();
^
Solution.java:9: error: <identifier> expected
System.out.println( Arrays.(a) );
^
7 errors
Code: 11:33:37 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
System.out.println( Arrays.(a) );
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
Compile error
Solution.java:9: error: <identifier> expected
System.out.println( Arrays.(a) );
^
1 error
Code: 11:33:51 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
System.out.println( Arrays.toString(a) );
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
Compile error
Solution.java:7: error: cannot find symbol
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
^
symbol: variable IntStream
location: class Solution
Solution.java:13: error: cannot find symbol
if( A[i] == next )
^
symbol: variable next
location: class Solution
Solution.java:14: error: cannot find symbol
next++;
^
symbol: variable next
location: class Solution
Solution.java:15: error: cannot find symbol
else if (A[i] > next)
^
symbol: variable next
location: class Solution
Solution.java:16: error: cannot find symbol
return next;
^
symbol: variable next
location: class Solution
Solution.java:19: error: cannot find symbol
return next;
^
symbol: variable next
location: class Solution
6 errors
Code: 11:34:10 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
System.out.println( Arrays.toString(a) );
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
Compile error
Solution.java:14: error: cannot find symbol
if( A[i] == next )
^
symbol: variable next
location: class Solution
Solution.java:15: error: cannot find symbol
next++;
^
symbol: variable next
location: class Solution
Solution.java:16: error: cannot find symbol
else if (A[i] > next)
^
symbol: variable next
location: class Solution
Solution.java:17: error: cannot find symbol
return next;
^
symbol: variable next
location: class Solution
Solution.java:20: error: cannot find symbol
return next;
^
symbol: variable next
location: class Solution
5 errors
Code: 11:34:24 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
int next = 1;
System.out.println( Arrays.toString(a) );
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.714 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1, 3, 6, 4, 2]
expand all
User tests
1.
1.608 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1]
1.
1.581 s
OK
function result: 1
function result: 1
stdout:
[]
1.
1.623 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1, 2, 4]
1.
1.634 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -4 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[4]
User test case 1:
[1, -1]
User test case 2:
[0, -2]
User test case 3:
[1, 2, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:35:01 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
int next = 1;
System.out.println( Arrays.toString(a) );
for (int i = Arrays.binarySearch(A, 0); i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.984 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1, 3, 6, 4, 2]
expand all
User tests
1.
1.985 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1]
1.
1.993 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -3 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1]
1.
1.938 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[1, 2, 4]
1.
1.590 s
RUNTIME ERROR,
tested program terminated unexpectedly
stderr:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -4 at Solution.solution(Solution.java:14) at wrapper.run(wrapper.java:40) at wrapper.main(wrapper.java:29)stdout:
[4]
User test case 1:
[1, -1]
User test case 2:
[0, -2, 1, -2]
User test case 3:
[1, 2, 4, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:36:20 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
Arrays.sort(a);
int next = 1;
for (int i = 0; i < A.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.628 s
WRONG ANSWER,
got 2 expected 5
expand all
User tests
1.
1.574 s
OK
function result: 2
function result: 2
1.
1.520 s
OK
function result: 2
function result: 2
1.
1.529 s
OK
function result: 3
function result: 3
1.
1.542 s
OK
function result: 1
function result: 1
User test case 1:
[1, -1]
User test case 2:
[0, -2, 1, -2]
User test case 3:
[1, 2, 4, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:37:21 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
Arrays.sort(a);
int next = 1;
for (int i = 0; i < a.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.527 s
WRONG ANSWER,
got 2 expected 5
expand all
User tests
1.
1.375 s
OK
function result: 2
function result: 2
1.
1.339 s
OK
function result: 1
function result: 1
1.
1.339 s
OK
function result: 3
function result: 3
1.
1.342 s
OK
function result: 1
function result: 1
User test case 1:
[1, -1]
User test case 2:
[0, -2, 1, -2]
User test case 3:
[1, 2, 4, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:37:52 UTC,
java,
verify,
result: Failed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
Arrays.sort(a);
int next = 1;
System.out.println(Arrays.toString(a));
for (int i = 0; i < a.length; i++ )
{
if( A[i] == next )
next++;
else if (A[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
Example tests
1.
1.583 s
WRONG ANSWER,
got 2 expected 5
stdout:
[1, 2, 3, 4, 6]
expand all
User tests
1.
1.606 s
OK
function result: 2
function result: 2
stdout:
[1]
1.
1.665 s
OK
function result: 1
function result: 1
stdout:
[1]
1.
1.613 s
OK
function result: 3
function result: 3
stdout:
[1, 2, 4]
1.
1.556 s
OK
function result: 1
function result: 1
stdout:
[4]
User test case 1:
[1, -1]
User test case 2:
[0, -2, 1, -2]
User test case 3:
[1, 2, 4, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:38:27 UTC,
java,
verify,
result: Passed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
Arrays.sort(a);
int next = 1;
for (int i = 0; i < a.length; i++ )
{
if( a[i] == next )
next++;
else if (a[i] > next)
return next;
}
return next;
}
}
Analysis
expand all
User tests
1.
1.965 s
OK
function result: 2
function result: 2
1.
1.964 s
OK
function result: 2
function result: 2
1.
1.970 s
OK
function result: 3
function result: 3
1.
1.977 s
OK
function result: 1
function result: 1
User test case 1:
[1, -1]
User test case 2:
[0, -2, 1, -2]
User test case 3:
[1, 2, 4, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:39:24 UTC,
java,
verify,
result: Passed
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
Arrays.sort(a);
int next = 1;
for (int i = 0; i < a.length; i++ )
{
if( a[i] == next )
next++;
else if ( a[i] > next)
break;
}
return next;
}
}
Analysis
expand all
User tests
1.
1.361 s
OK
function result: 2
function result: 2
1.
1.781 s
OK
function result: 2
function result: 2
1.
1.940 s
OK
function result: 3
function result: 3
1.
1.956 s
OK
function result: 1
function result: 1
User test case 1:
[1, -1]
User test case 2:
[0, -2, 1, -2]
User test case 3:
[1, 2, 4, 4]
User test case 4:
[-5, -2, -3, 4]
Code: 11:39:36 UTC,
java,
final,
score:
88
import java.util.Arrays;
import java.util.stream.*;
class Solution
{
public int solution(int[] A)
{
int[] a = IntStream.of(A).distinct().filter( s -> s > 0 ).toArray();
Arrays.sort(a);
int next = 1;
for (int i = 0; i < a.length; i++ )
{
if( a[i] == next )
next++;
else if ( a[i] > next)
break;
}
return next;
}
}Analysis summary
The following issues have been detected: timeout errors.
Analysis
Detected time complexity:
O(N)
expand all
Correctness tests
1.
1.966 s
OK
2.
1.955 s
OK
3.
1.966 s
OK
1.
1.938 s
OK
2.
1.708 s
OK
1.
1.961 s
OK
2.
1.961 s
OK
1.
1.946 s
OK
1.
1.961 s
OK
expand all
Performance tests
medium
chaotic sequences length=10005 (with minus)
chaotic sequences length=10005 (with minus)
✘
TIMEOUT ERROR
running time: 1.93 sec., time limit: 1.50 sec.
running time: 1.93 sec., time limit: 1.50 sec.
1.
1.950 s
OK
2.
1.929 s
TIMEOUT ERROR,
running time: 1.93 sec., time limit: 1.50 sec.
3.
2.031 s
OK
1.
2.482 s
OK
1.
2.643 s
OK
2.
2.636 s
OK
1.
2.304 s
OK