MinAvgTwoSlice.md

Task description A non-empty zero-indexed array A consisting of N integers is given. A pair of integers (P, Q), such that 0 ≤ P < Q < N, is called a slice of array A (notice that the slice contains at least two elements). The average of a slice (P, Q) is the sum of A[P] + A[P + 1] + ... + A[Q] divided by the length of the slice. To be precise, the average equals (A[P] + A[P + 1] + ... + A[Q]) / (Q − P + 1).

For example, array A such that:

    A[0] = 4
    A[1] = 2
    A[2] = 2
    A[3] = 5
    A[4] = 1
    A[5] = 5
    A[6] = 8

contains the following example slices:

slice (1, 2), whose average is (2 + 2) / 2 = 2; slice (3, 4), whose average is (5 + 1) / 2 = 3; slice (1, 4), whose average is (2 + 2 + 5 + 1) / 4 = 2.5. The goal is to find the starting position of a slice whose average is minimal.

Write a function:

function solution(A);

that, given a non-empty zero-indexed array A consisting of N integers, returns the starting position of the slice with the minimal average. If there is more than one slice with a minimal average, you should return the smallest starting position of such a slice.

function solution(A) {
   var start = 0;

   var currentSum = A[0] + A[1];
   var minAvgSlice = currentSum / 2;
   for (var i=2; i<A.length; i++) {
      currentSum += A[i];
      var newAvg = currentSum / 3;
      if (newAvg < minAvgSlice) {
         minAvgSlice = newAvg;
         start = i-2;
      }

      currentSum -= A[i-2];
      newAvg = currentSum / 2;
      if (newAvg < minAvgSlice) {
         minAvgSlice = newAvg;
         start = i-1;
      }
   }

   return start;
}