[codility]AbsDistinct

Task description

A non-empty zero-indexed array A consisting of N numbers is given. The array is sorted in non-decreasing order. The absolute distinct count of this array is the number of distinct absolute values among the elements of the array.

For example, consider array A such that:

  A[0] = -5  A[1] = -3  A[2] = -1  A[3] =  0  A[4] =  3  A[5] =  6

The absolute distinct count of this array is 5, because there are 5 distinct absolute values among the elements of this array, namely 0, 1, 3, 5 and 6.

Write a function:

int solution(vector<int> &A);

that, given a non-empty zero-indexed array A consisting of N numbers, returns absolute distinct count of array A.

For example, given array A such that:

  A[0] = -5  A[1] = -3  A[2] = -1  A[3] =  0  A[4] =  3  A[5] =  6

the function should return 5, as explained above.

Assume that:

• N is an integer within the range [1..100,000];
• each element of array A is an integer within the range [−2,147,483,648..2,147,483,647];
• array A is sorted in non-decreasing order.

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.

// you can use includes, for example:// #include <algorithm>#include <cstdlib>// you can write to stdout for debugging purposes, e.g.// cout << "this is a debug message" << endl;int solution(vector<int> &A) {    // write your code in C++11    long long prev_absolute_value = -1;    int ret = 0;    for(int i = 0, j = A.size()-1; i <= j; ) {        //avoid arith overflow, abs(INT_MIN) overflow        long long left_absolute_value   = llabs(A[i]);         long long right_absolute_value  = llabs(A[j]);                if(left_absolute_value > right_absolute_value) {            if(left_absolute_value != prev_absolute_value) {                ret++;                prev_absolute_value = left_absolute_value;            }            i++;        }        else {            if(right_absolute_value != prev_absolute_value) {                ret++;                prev_absolute_value = right_absolute_value;            }            j--;        }    }    return ret;}