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:
function solution(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 JavaScript
Time spent on task 18 minutes
Notes
not defined yet
Code: 11:28:37 UTC,
java,
autosave
Code: 11:45:09 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
const counters = new Array(A.length).fill(false);
for (let i = 0; i < A.length; i++) {
const index = A[i] - 1;
if (counters[index] === false) {
counters[index] = true;
}
}
for (let i = 0; i < counters.length; i++) {
const element = counters[i];
if (element === false) {
return i + 1;
}
}
return A.length + 1;
}
Code: 11:45:09 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
const counters = new Array(A.length).fill(false);
for (let i = 0; i < A.length; i++) {
const index = A[i] - 1;
if (counters[index] === false) {
counters[index] = true;
}
}
for (let i = 0; i < counters.length; i++) {
const element = counters[i];
if (element === false) {
return i + 1;
}
}
return A.length + 1;
}
Analysis
Code: 11:45:36 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
const counters = new Array(A.length).fill(false);
for (let i = 0; i < A.length; i++) {
const index = A[i] - 1;
if (counters[index] === false) {
counters[index] = true;
}
}
for (let i = 0; i < counters.length; i++) {
const element = counters[i];
if (element === false) {
return i + 1;
}
}
return A.length + 1;
}
Analysis
Code: 11:45:39 UTC,
js,
final,
score:
100
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
const counters = new Array(A.length).fill(false);
for (let i = 0; i < A.length; i++) {
const index = A[i] - 1;
if (counters[index] === false) {
counters[index] = true;
}
}
for (let i = 0; i < counters.length; i++) {
const element = counters[i];
if (element === false) {
return i + 1;
}
}
return A.length + 1;
}
Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Correctness tests
1.
0.072 s
OK
2.
0.068 s
OK
3.
0.072 s
OK
4.
0.072 s
OK
1.
0.068 s
OK
2.
0.068 s
OK
3.
0.068 s
OK
1.
0.072 s
OK
2.
0.068 s
OK
1.
0.072 s
OK
2.
0.068 s
OK
1.
0.072 s
OK
expand all
Performance tests
1.
0.092 s
OK
2.
0.084 s
OK
3.
0.084 s
OK
1.
0.112 s
OK
1.
0.112 s
OK
2.
0.112 s
OK
1.
0.108 s
OK