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 15 minutes
Notes
not defined yet
Code: 14:13:58 UTC,
java,
autosave
Code: 14:22:48 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max(A);
if (max < 0) return 1;
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Code: 14:22:48 UTC,
js,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max(A);
if (max < 0) return 1;
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
expand all
Example tests
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
RangeError: Invalid array length at solution (solution.js:7:11) at solutionWrapper (/tmp/exec.js:402:28) at Promise.resolve.then (/tmp/exec.js:428:24) at <anonymous> at process._tickCallback (internal/process/next_tick.js:188:7) at Function.Module.runMain (module.js:686:11) at startup (bootstrap_node.js:187:16) at bootstrap_node.js:608:3
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
RangeError: Invalid array length at solution (solution.js:7:11) at solutionWrapper (/tmp/exec.js:402:28) at Promise.resolve.then (/tmp/exec.js:428:24) at <anonymous> at process._tickCallback (internal/process/next_tick.js:188:7) at Function.Module.runMain (module.js:686:11) at startup (bootstrap_node.js:187:16) at bootstrap_node.js:608:3
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
RangeError: Invalid array length at solution (solution.js:7:11) at solutionWrapper (/tmp/exec.js:402:28) at Promise.resolve.then (/tmp/exec.js:428:24) at <anonymous> at process._tickCallback (internal/process/next_tick.js:188:7) at Function.Module.runMain (module.js:686:11) at startup (bootstrap_node.js:187:16) at bootstrap_node.js:608:3
Code: 14:24:06 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max(A);
if (max < 0) return 1;
co
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Code: 14:24:16 UTC,
js,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max(A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
expand all
Example tests
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
RangeError: Invalid array length at solution (solution.js:8:11) at solutionWrapper (/tmp/exec.js:402:28) at Promise.resolve.then (/tmp/exec.js:428:24) at <anonymous> at process._tickCallback (internal/process/next_tick.js:188:7) at Function.Module.runMain (module.js:686:11) at startup (bootstrap_node.js:187:16) at bootstrap_node.js:608:3stdout:
NaN
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
RangeError: Invalid array length at solution (solution.js:8:11) at solutionWrapper (/tmp/exec.js:402:28) at Promise.resolve.then (/tmp/exec.js:428:24) at <anonymous> at process._tickCallback (internal/process/next_tick.js:188:7) at Function.Module.runMain (module.js:686:11) at startup (bootstrap_node.js:187:16) at bootstrap_node.js:608:3stdout:
NaN
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
RangeError: Invalid array length at solution (solution.js:8:11) at solutionWrapper (/tmp/exec.js:402:28) at Promise.resolve.then (/tmp/exec.js:428:24) at <anonymous> at process._tickCallback (internal/process/next_tick.js:188:7) at Function.Module.runMain (module.js:686:11) at startup (bootstrap_node.js:187:16) at bootstrap_node.js:608:3stdout:
NaN
Code: 14:26:13 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max.(A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Code: 14:26:22 UTC,
js,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
expand all
Example tests
1.
0.076 s
WRONG ANSWER,
got 7 expected 5
stdout:
6
1.
0.076 s
OK
stdout:
3
1.
0.072 s
OK
Code: 14:26:43 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
console.log(index)
console.log(B)
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Code: 14:26:45 UTC,
js,
verify,
result: Failed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
console.log(index)
console.log(B)
if ((index = -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
expand all
Example tests
1.
0.072 s
WRONG ANSWER,
got 7 expected 5
stdout:
6 4 [ 2, 1, 1, 1, 0, 1 ]
1.
0.072 s
OK
stdout:
3 -1 [ 1, 1, 1 ]
1.
0.068 s
OK
Code: 14:27:17 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
console.log(index)
console.log(B)
if ((index === -1)) {
return max + 1;
} else {
return index + 1;
}
}
Code: 14:27:18 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) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
console.log(index)
console.log(B)
if ((index === -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
expand all
Example tests
1.
0.072 s
OK
stdout:
6 4 [ 2, 1, 1, 1, 0, 1 ]
1.
0.072 s
OK
stdout:
3 -1 [ 1, 1, 1 ]
1.
0.068 s
OK
Code: 14:28:16 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
console.log(max);
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
console.log(index)
if ((index === -1)) {
return max + 1;
} else {
return index + 1;
}
}
Code: 14:28:24 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) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index === -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
Code: 14:28:30 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) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index === -1)) {
return max + 1;
} else {
return index + 1;
}
}
Analysis
Code: 14:28:33 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) {
let max = Math.max.apply(null,A);
if (max < 0) return 1;
let B = new Array(max).fill(0);
for (let i = 0; i < A.length; i++) {
if (A[i] > 0) {
B[A[i] - 1]++;
}
}
let index = B.indexOf(0);
if ((index === -1)) {
return max + 1;
} else {
return index + 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.
0.072 s
OK
3.
0.072 s
OK
4.
0.072 s
OK
1.
0.072 s
OK
2.
0.072 s
OK
3.
0.072 s
OK
1.
0.100 s
OK
2.
0.100 s
OK
1.
0.072 s
OK
2.
0.072 s
OK
1.
0.072 s
OK
expand all
Performance tests
1.
0.084 s
OK
2.
0.080 s
OK
3.
0.116 s
OK
1.
0.112 s
OK
1.
0.120 s
OK
2.
0.116 s
OK
1.
0.136 s
OK