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:
class Solution { public int solution(int[] 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 C#
Time spent on task 1 minutes
Notes
not defined yet
Code: 14:11:45 UTC,
cs,
verify,
result: Passed
using System;
// you can also use other imports, for example:
using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
var set = new HashSet<int>();
var max = int.MinValue;
foreach (var item in A)
{
if (set.Contains(item)) return 0;
set.Add(item);
if (item > max) max = item;
}
return set.Count == max ? 1 : 0;
}
}
Analysis
Code: 14:11:48 UTC,
cs,
verify,
result: Passed
using System;
// you can also use other imports, for example:
using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
var set = new HashSet<int>();
var max = int.MinValue;
foreach (var item in A)
{
if (set.Contains(item)) return 0;
set.Add(item);
if (item > max) max = item;
}
return set.Count == max ? 1 : 0;
}
}
Analysis
Code: 14:11:51 UTC,
cs,
final,
score:
100
using System;
// you can also use other imports, for example:
using System.Collections.Generic;
// you can use Console.WriteLine for debugging purposes, e.g.
// Console.WriteLine("this is a debug message");
class Solution {
public int solution(int[] A) {
var set = new HashSet<int>();
var max = int.MinValue;
foreach (var item in A)
{
if (set.Contains(item)) return 0;
set.Add(item);
if (item > max) max = item;
}
return set.Count == max ? 1 : 0;
}
}Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Correctness tests
1.
0.068 s
OK
2.
0.069 s
OK
1.
0.069 s
OK
2.
0.069 s
OK
1.
0.068 s
OK
2.
0.069 s
OK
3.
0.069 s
OK
4.
0.069 s
OK
1.
0.069 s
OK
2.
0.069 s
OK
3.
0.070 s
OK
4.
0.069 s
OK
1.
0.070 s
OK
2.
0.070 s
OK
expand all
Performance tests
1.
0.075 s
OK
2.
0.074 s
OK
1.
0.103 s
OK
2.
0.114 s
OK
1.
0.117 s
OK
2.
0.117 s
OK
1.
0.115 s
OK
2.
0.115 s
OK
1.
0.070 s
OK
2.
0.092 s
OK
3.
0.070 s
OK