Tasks Details
medium
Find the smallest positive integer that does not occur in a given sequence.
Task Score
100%
Correctness
100%
Performance
100%
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 8
Time spent on task 1 minutes
Notes
not defined yet
Code: 17:41:28 UTC,
java,
autosave
Code: 17:41:39 UTC,
java,
autosave
// you can also use imports, for example:
import java.util.Arrays;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] array) {
boolean[] nums = new boolean[1000001];
Arrays.stream(array).forEach(i -> {
if(i > 0) {
nums[i] = true;
}
});
if(!nums[1])
return 1;
for(int i = 2; i < nums.length; i++) {
if(!nums[i])
return i;
}
return 1;
}
}
Code: 17:41:44 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
import java.util.Arrays;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] array) {
boolean[] nums = new boolean[1000001];
Arrays.stream(array).forEach(i -> {
if(i > 0) {
nums[i] = true;
}
});
if(!nums[1])
return 1;
for(int i = 2; i < nums.length; i++) {
if(!nums[i])
return i;
}
return 1;
}
}
Analysis
Code: 17:41:51 UTC,
java,
final,
score:
100
// you can also use imports, for example:
import java.util.Arrays;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] array) {
boolean[] nums = new boolean[1000001];
Arrays.stream(array).forEach(i -> {
if(i > 0) {
nums[i] = true;
}
});
if(!nums[1])
return 1;
for(int i = 2; i < nums.length; i++) {
if(!nums[i])
return i;
}
return 1;
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Correctness tests
1.
0.012 s
OK
2.
0.012 s
OK
3.
0.012 s
OK
4.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
3.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
1.
0.012 s
OK
2.
0.012 s
OK
1.
0.012 s
OK
expand all
Performance tests
1.
0.032 s
OK
2.
0.028 s
OK
3.
0.040 s
OK
1.
0.232 s
OK
1.
0.260 s
OK
2.
0.256 s
OK
1.
0.188 s
OK