Test results - Codility

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] = 2

is a permutation, but array A such that:

A[0] = 4 A[1] = 1 A[2] = 3

is 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] = 2

the function should return 1.

Given array A such that:

A[0] = 4 A[1] = 1 A[2] = 3

the 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].

Solution

Programming language used Java 8

Time spent on task 2 minutes

Notes

not defined yet

Code: 19:51:04 UTC, java, autosave

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// 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) {
        return isPermutation(A) ? 1 : 0;
    }

    private static boolean isPermutation(int[] A) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();
        for (int i = 0; i < A.length; i++) {
            set1.add(A[i]);
            set2.add(i + 1);
        }
        set2.removeAll(set1);
        return set2.isEmpty();
    }
}

Code: 19:51:14 UTC, java, autosave

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// 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) {
        return isPermutation(A) ? 1 : 0;
    }

    private boolean isPermutation(int[] A) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();
        for (int i = 0; i < A.length; i++) {
            set1.add(A[i]);
            set2.add(i + 1);
        }
        set2.removeAll(set1);
        return set2.isEmpty();
    }
}

Code: 19:51:47 UTC, java, autosave

show code in pop-up

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// you can also use imports, for example:
import java.util.HashSet;
import java.util.Set;

// 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) {
        return isPermutation(A) ? 1 : 0;
    }

    private boolean isPermutation(int[] A) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();
        for (int i = 0; i < A.length; i++) {
            set1.add(A[i]);
            set2.add(i + 1);
        }
        set2.removeAll(set1);
        return set2.isEmpty();
    }
}

Code: 19:52:08 UTC, java, verify, result: Passed

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// you can also use imports, for example:
import java.util.HashSet;
import java.util.Set;

// 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) {
        return isPermutation(A) ? 1 : 0;
    }

    private boolean isPermutation(int[] A) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();
        for (int i = 0; i < A.length; i++) {
            set1.add(A[i]);
            set2.add(i + 1);
        }
        set2.removeAll(set1);
        return set2.isEmpty();
    }
}

Analysis

expand all Example tests

▶

example1
the first example test

✔

0.008 s

▶

example2
the second example test

✔

0.008 s

Code: 19:52:16 UTC, java, verify, result: Passed

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

// you can also use imports, for example:
import java.util.HashSet;
import java.util.Set;

// 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) {
        return isPermutation(A) ? 1 : 0;
    }

    private boolean isPermutation(int[] A) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();
        for (int i = 0; i < A.length; i++) {
            set1.add(A[i]);
            set2.add(i + 1);
        }
        set2.removeAll(set1);
        return set2.isEmpty();
    }
}

Analysis

expand all Example tests

▶

example1
the first example test

✔

0.008 s

▶

example2
the second example test

✔

0.008 s

Code: 19:52:21 UTC, java, final, score: 100

show code in pop-up

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

// you can also use imports, for example:
import java.util.HashSet;
import java.util.Set;

// 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) {
        return isPermutation(A) ? 1 : 0;
    }

    private boolean isPermutation(int[] A) {
        Set<Integer> set1 = new HashSet<>();
        Set<Integer> set2 = new HashSet<>();
        for (int i = 0; i < A.length; i++) {
            set1.add(A[i]);
            set2.add(i + 1);
        }
        set2.removeAll(set1);
        return set2.isEmpty();
    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N) or O(N * log(N))

expand all Example tests

▶

example1
the first example test

✔

0.004 s

▶

example2
the second example test

✔

0.008 s

expand all Correctness tests

▶

extreme_min_max
single element with minimal/maximal value

✔

0.004 s

▶

single
single element

✔

0.004 s

▶

double
two elements

✔

0.004 s

▶

antiSum1
total sum is correct, but it is not a permutation, N <= 10

✔

0.004 s

▶

small_permutation
permutation + one element occurs twice, N = ~100

✔

0.004 s

0.008 s

▶

permutations_of_ranges
permutations of sets like [2..100] for which the anwsers should be false

✔

0.004 s

0.008 s

expand all Performance tests

▶

medium_permutation
permutation + few elements occur twice, N = ~10,000

✔

0.068 s

▶

antiSum2
total sum is correct, but it is not a permutation, N = ~100,000

✔

0.660 s

0.668 s

▶

large_not_permutation
permutation + one element occurs three times, N = ~100,000

✔

0.684 s

0.676 s

▶

large_range
sequence 1, 2, ..., N, N = ~100,000

✔

0.756 s

▶

extreme_values
all the same values, N = ~100,000

✔

0.004 s

0.392 s

0.004 s

▶

various_permutations
all sequences are permutations

✔

0.008 s

0.076 s

0.756 s

0.768 s