środa, 6 maja 2015

Codility solutions - lesson2, exercise: PermCheck

Check whether array A is a permutation.

Content of Codility exercise:

A non-empty zero-indexed 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 a zero-indexed 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.

Assume that:

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].
Complexity:

expected worst-case time complexity is O(N);
expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).
Elements of input arrays can be modified.

Solution:

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    public int solution(int[] A) {
        int N = A.length;
        //create tmp array to store information about each number occurrence
        int tmbB[] = new int[A.length];
        int element = 0;
        for (int i = 0; i < A.length; i++){
            element = A[i];
            //if element is greater than array A length it is obvious that A isn't permutation
            if (element> N){
                return 0;
            }
            tmbB[element-1]++;
        }
        //index where number in array is equal zero, is our missing element
        //and array A isn't permutation
        if (isContainZeroElement(tmbB)){
            return 0;
        }else {
            return 1;
        }
    }

    private boolean isContainZeroElement(int [] B){
        for (int element: B){
            if (element == 0){
                return true;
            }
        }
        return false;
    }

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