Tasks Details
easy
1.
PermCheck
Check whether array A is a permutation.
Task Score
100%
Correctness
100%
Performance
100%
A non-empty array A consisting of N integers is given.
A permutation is a sequence containing each element from 1 to N once, and only once.
For example, array A such that:
A[0] = 4 A[1] = 1 A[2] = 3 A[3] = 2is a permutation, but array A such that:
A[0] = 4 A[1] = 1 A[2] = 3is not a permutation, because value 2 is missing.
The goal is to check whether array A is a permutation.
Write a function:
function solution(A);
that, given an array A, returns 1 if array A is a permutation and 0 if it is not.
For example, given array A such that:
A[0] = 4 A[1] = 1 A[2] = 3 A[3] = 2the function should return 1.
Given array A such that:
A[0] = 4 A[1] = 1 A[2] = 3the function should return 0.
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..1,000,000,000].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used JavaScript
Time spent on task 5 minutes
Notes
not defined yet
Code: 10:54:47 UTC,
java,
autosave
Code: 10:57:08 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
retu
}
}
}
Code: 10:57:12 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) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
return false;
}
}
return true;
}
Analysis
expand all
Example tests
1.
0.072 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Invalid result type, integer expected, 'boolean' found
1.
0.068 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Invalid result type, integer expected, 'boolean' found
Code: 10:57:26 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) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
return 0;
}
}
return 1;
}
Analysis
Code: 10:57:59 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
return 0;
}
}
return 1;
}
Code: 10:58:24 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) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
return 0;
}
}
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Analysis
Code: 10:58:37 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
const N = A.length;
const counter = new Array(N).fill(false);
c
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
return 0;
}
}
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Code: 10:58:47 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) {
const N = A.length;
const counter = new Array(N).fill(false);
console.log(counter);
for (let i = 0; i < N; i++) {
if (!counter[A[i]]) {
counter[A[i]] = true;
} else {
return 0;
}
}
console.log(counter);
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Analysis
expand all
Example tests
1.
0.072 s
WRONG ANSWER,
got 0 expected 1
stdout:
[ false, false, false, false ] [ false, true, true, true, true ]
1.
0.072 s
OK
stdout:
[ false, false, false ] [ false, true, false, true, true ]
Code: 10:59:06 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) {
const N = A.length;
const counter = new Array(N).fill(false);
console.log(counter);
for (let i = 0; i < N; i++) {
if (!counter[A[i] - 1]) {
counter[A[i] - 1] = true;
} else {
return 0;
}
}
console.log(counter);
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Analysis
expand all
Example tests
1.
0.076 s
OK
stdout:
[ false, false, false, false ] [ true, true, true, true ]
1.
0.076 s
OK
stdout:
[ false, false, false ] [ true, false, true, true ]
Code: 10:59:14 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
const N = A.length;
const counter = new Array(N).fill(false);
console.log(counter);
for (let i = 0; i < N; i++) {
if (!counter[A[i] - 1]) {
counter[A[i] - 1] = true;
} else {
return 0;
}
}
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Code: 10:59:16 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) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i] - 1]) {
counter[A[i] - 1] = true;
} else {
return 0;
}
}
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Analysis
Code: 10:59:19 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) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i] - 1]) {
counter[A[i] - 1] = true;
} else {
return 0;
}
}
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
return 1;
}
Analysis
Code: 10:59:21 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) {
const N = A.length;
const counter = new Array(N).fill(false);
for (let i = 0; i < N; i++) {
if (!counter[A[i] - 1]) {
counter[A[i] - 1] = true;
} else {
return 0;
}
}
for (let i = 0; i < N; i++) {
if (!counter[i]) {
return 0;
}
}
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.
0.072 s
OK
2.
0.072 s
OK
1.
0.072 s
OK
2.
0.072 s
OK
1.
0.076 s
OK
2.
0.072 s
OK
3.
0.072 s
OK
4.
0.072 s
OK
1.
0.072 s
OK
2.
0.076 s
OK
3.
0.072 s
OK
4.
0.072 s
OK
1.
0.072 s
OK
2.
0.072 s
OK
permutations_of_ranges
permutations of sets like [2..100] for which the anwsers should be false
permutations of sets like [2..100] for which the anwsers should be false
✔
OK
1.
0.072 s
OK
2.
0.072 s
OK
3.
0.072 s
OK
expand all
Performance tests
1.
0.084 s
OK
2.
0.084 s
OK
1.
0.112 s
OK
2.
0.116 s
OK
1.
0.116 s
OK
2.
0.116 s
OK
1.
0.116 s
OK
2.
0.128 s
OK
1.
0.072 s
OK
2.
0.100 s
OK
3.
0.072 s
OK
1.
0.072 s
OK
2.
0.072 s
OK
3.
0.084 s
OK
4.
0.120 s
OK
5.
0.128 s
OK