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 21
Time spent on task 1 minutes
Notes
not defined yet
Code: 09:09:45 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
// import java.util.*;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
boolean[] B = new boolean[1000001];
java.util.Arrays.fill(B, false);
for (int i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i]] = true;
}
}
for (int j = 1; j < B.length; j++) {
if (!B[j]) return j;
}
return 1000001;
}
}
Analysis
Code: 09:09:50 UTC,
java,
final,
score:
100
// you can also use imports, for example:
// import java.util.*;
// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int[] A) {
boolean[] B = new boolean[1000001];
java.util.Arrays.fill(B, false);
for (int i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i]] = true;
}
}
for (int j = 1; j < B.length; j++) {
if (!B[j]) return j;
}
return 1000001;
}
}
Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Correctness tests
1.
0.020 s
OK
2.
0.020 s
OK
3.
0.016 s
OK
4.
0.020 s
OK
1.
0.020 s
OK
2.
0.016 s
OK
3.
0.020 s
OK
1.
0.020 s
OK
2.
0.020 s
OK
1.
0.020 s
OK
2.
0.020 s
OK
1.
0.020 s
OK
expand all
Performance tests
1.
0.040 s
OK
2.
0.036 s
OK
3.
0.048 s
OK
1.
0.236 s
OK
1.
0.264 s
OK
2.
0.260 s
OK
1.
0.188 s
OK