Tuesday, August 11, 2015

Codility Max Counters

Problem

You are given N counters, initially set to 0, and you have two possible operations on them:
    increase(X)  counter X is increased by 1,
    max_counter  all counters are set to the maximum value of any counter.
A non-empty zero-indexed array A of M integers is given. This array represents consecutive operations:
    if A[K] = X, such that 1  X  N, then operation K is increase(X),
    if A[K] = N + 1 then operation K is max_counter.
For example, given integer N = 5 and array A such that:
A[0] = 3
A[1] = 4
A[2] = 4
A[3] = 6
A[4] = 1
A[5] = 4
A[6] = 4
the values of the counters after each consecutive operation will be:
(0, 0, 1, 0, 0)
(0, 0, 1, 1, 0)
(0, 0, 1, 2, 0)
(2, 2, 2, 2, 2)
(3, 2, 2, 2, 2)
(3, 2, 2, 3, 2)
(3, 2, 2, 4, 2)
The goal is to calculate the value of every counter after all operations.
struct Results {
  int * C;
  int L;
}; 
Write a function:
struct Results solution(int N, int A[], int M); 
that, given an integer N and a non-empty zero-indexed array A consisting of M integers, returns a sequence of integers representing the values of the counters.
The sequence should be returned as:
    a structure Results (in C), or
    a vector of integers (in C++), or
    a record Results (in Pascal), or
    an array of integers (in any other programming language).
For example, given:
A[0] = 3
A[1] = 4
A[2] = 4
A[3] = 6
A[4] = 1
A[5] = 4
A[6] = 4
the function should return [3, 2, 2, 4, 2], as explained above.
Assume that:
    N and M are integers within the range [1..100,000];
    each element of array A is an integer within the range [1..N + 1].
Complexity:
    expected worst-case time complexity is O(N+M);
    expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).

Solution

 public int[] solution(int N, int[] A) 
 {
  int[] counters = new int[N];
  int maxValue = 0, lastUpdatedValue= 0;
  int index=0;

  for(int i=0; i< A.length; i++)
  {
   if(A[i] == (N+1))
   {
    lastUpdatedValue = maxValue;
   }
   else 
   {
    index = (A[i]-1);
    if(counters[index] < lastUpdatedValue)
     counters[index] = lastUpdatedValue;
    counters[index]++;
    if(maxValue < counters[index]) maxValue = counters[index];
   }
  }
  for(index=0; index< N; index++)
  {
   if(counters[index]< lastUpdatedValue) counters[index] = lastUpdatedValue;
  }
  return counters;
 }

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