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: 10:42:32 UTC,
java,
autosave
Code: 10:42:43 UTC,
java,
autosave
// 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) {
int smallestPositiveInteger = 1;
int maxValue = 0;
boolean allValuesAreNegative = true;
Arrays.sort(A);
Set<Integer> set = new HashSet<>();
for (int value : A) {
if (value > 0) {
set.add(value);
allValuesAreNegative = false;
if (value > maxValue) {
maxValue = value;
}
}
}
if (!allValuesAreNegative) {
boolean smallestPositiveIntegerFinded = false;
int i = 1;
while(!smallestPositiveIntegerFinded && i < maxValue) {
if (!set.contains(i)) {
smallestPositiveIntegerFinded = true;
smallestPositiveInteger = i;
}
i++;
}
if (!smallestPositiveIntegerFinded) {
smallestPositiveInteger = maxValue + 1;
}
}
System.out.println("Missing integer is: " + smallestPositiveInteger);
return smallestPositiveInteger;
}
}
Code: 10:42:50 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) {
int smallestPositiveInteger = 1;
int maxValue = 0;
boolean allValuesAreNegative = true;
Arrays.sort(A);
Set<Integer> set = new HashSet<>();
for (int value : A) {
if (value > 0) {
set.add(value);
allValuesAreNegative = false;
if (value > maxValue) {
maxValue = value;
}
}
}
if (!allValuesAreNegative) {
boolean smallestPositiveIntegerFinded = false;
int i = 1;
while(!smallestPositiveIntegerFinded && i < maxValue) {
if (!set.contains(i)) {
smallestPositiveIntegerFinded = true;
smallestPositiveInteger = i;
}
i++;
}
if (!smallestPositiveIntegerFinded) {
smallestPositiveInteger = maxValue + 1;
}
}
return smallestPositiveInteger;
}
}
Analysis
Code: 10:42:57 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) {
int smallestPositiveInteger = 1;
int maxValue = 0;
boolean allValuesAreNegative = true;
Arrays.sort(A);
Set<Integer> set = new HashSet<>();
for (int value : A) {
if (value > 0) {
set.add(value);
allValuesAreNegative = false;
if (value > maxValue) {
maxValue = value;
}
}
}
if (!allValuesAreNegative) {
boolean smallestPositiveIntegerFinded = false;
int i = 1;
while(!smallestPositiveIntegerFinded && i < maxValue) {
if (!set.contains(i)) {
smallestPositiveIntegerFinded = true;
smallestPositiveInteger = i;
}
i++;
}
if (!smallestPositiveIntegerFinded) {
smallestPositiveInteger = maxValue + 1;
}
}
return smallestPositiveInteger;
}
}
Analysis
Code: 10:43:03 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) {
int smallestPositiveInteger = 1;
int maxValue = 0;
boolean allValuesAreNegative = true;
Arrays.sort(A);
Set<Integer> set = new HashSet<>();
for (int value : A) {
if (value > 0) {
set.add(value);
allValuesAreNegative = false;
if (value > maxValue) {
maxValue = value;
}
}
}
if (!allValuesAreNegative) {
boolean smallestPositiveIntegerFinded = false;
int i = 1;
while(!smallestPositiveIntegerFinded && i < maxValue) {
if (!set.contains(i)) {
smallestPositiveIntegerFinded = true;
smallestPositiveInteger = i;
}
i++;
}
if (!smallestPositiveIntegerFinded) {
smallestPositiveInteger = maxValue + 1;
}
}
return smallestPositiveInteger;
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Correctness tests
1.
0.004 s
OK
2.
0.008 s
OK
3.
0.008 s
OK
4.
0.008 s
OK
1.
0.008 s
OK
2.
0.008 s
OK
3.
0.008 s
OK
1.
0.004 s
OK
2.
0.008 s
OK
1.
0.008 s
OK
2.
0.008 s
OK
1.
0.008 s
OK
expand all
Performance tests
1.
0.032 s
OK
2.
0.028 s
OK
3.
0.044 s
OK
1.
0.416 s
OK
1.
0.540 s
OK
2.
0.492 s
OK
1.
0.272 s
OK