13 MinAvgTwoSlice

/*------------------------------------------------
A non-empty 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).

The goal is to find the starting position of a slice whose average is minimal.

Write a function that, given a non-empty 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.
------------------------------------------------*/

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    let minimalAverage = (A[0] + A[1]) / 2;
    let startingPosition = 0;
    
    for (let i=1; i<A.length; i+=1) {
        let currentDoubleAvg = (A[i] + A[i+1])/2;
        let currentTripleAvg = (A[i] + A[i+1] + A[i+2])/3;
        
        if (i+1 < A.length && currentDoubleAvg < minimalAverage) {
            minimalAverage = currentDoubleAvg;
            startingPosition = i;
        }
        
        if (i+2 < A.length && currentTripleAvg < minimalAverage) {
            minimalAverage = currentTripleAvg;
            startingPosition = i;
        }
    }
    
    return startingPosition;
}