peaks.js

/**
A non-empty zero-indexed array A consisting of N integers is given.
A peak is an array element which is larger than its neighbors. More precisely, it is an index P such that 0 < P < N − 1,  A[P − 1] < A[P] and A[P] > A[P + 1].
For example, the following array A:
    A[0] = 1
    A[1] = 2
    A[2] = 3
    A[3] = 4
    A[4] = 3
    A[5] = 4
    A[6] = 1
    A[7] = 2
    A[8] = 3
    A[9] = 4
    A[10] = 6
    A[11] = 2
has exactly three peaks: 3, 5, 10.
We want to divide this array into blocks containing the same number of elements. More precisely, we want to choose a number K that will yield the following blocks:
A[0], A[1], ..., A[K − 1],
A[K], A[K + 1], ..., A[2K − 1],
...
A[N − K], A[N − K + 1], ..., A[N − 1].
What's more, every block should contain at least one peak. Notice that extreme elements of the blocks (for example A[K − 1] or A[K]) can also be peaks, but only if they have both neighbors (including one in an adjacent blocks).
The goal is to find the maximum number of blocks into which the array A can be divided.
Array A can be divided into blocks as follows:
one block (1, 2, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2). This block contains three peaks.
two blocks (1, 2, 3, 4, 3, 4) and (1, 2, 3, 4, 6, 2). Every block has a peak.
three blocks (1, 2, 3, 4), (3, 4, 1, 2), (3, 4, 6, 2). Every block has a peak. Notice in particular that the first block (1, 2, 3, 4) has a peak at A[3], because A[2] < A[3] > A[4], even though A[4] is in the adjacent block.
However, array A cannot be divided into four blocks, (1, 2, 3), (4, 3, 4), (1, 2, 3) and (4, 6, 2), because the (1, 2, 3) blocks do not contain a peak. Notice in particular that the (4, 3, 4) block contains two peaks: A[3] and A[5].
The maximum number of blocks that array A can be divided into is three.
Write a function:
function solution(A);
that, given a non-empty zero-indexed array A consisting of N integers, returns the maximum number of blocks into which A can be divided.
If A cannot be divided into some number of blocks, the function should return 0.
For example, given:
    A[0] = 1
    A[1] = 2 
    A[2] = 3 
    A[3] = 4 
    A[4] = 3 
    A[5] = 4 
    A[6] = 1 
    A[7] = 2 
    A[8] = 3 
    A[9] = 4 
    A[10] = 6 
    A[11] = 2
the function should return 3, 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 [0..1,000,000,000].
Complexity:
expected worst-case time complexity is O(N*log(log(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.
**/

function solution(A) {
    var longitud = A.length;
    var peaks = [];
    var current = 0;
    for (i=1; i<longitud-1; i++){
        if((A[i-1]<A[i]) && (A[i]>A[i+1])){//here we get the index of the peak numbers
            peaks.push(i);
        }
    }
    for(i=0;i<longitud;i++){
        k=i+1; //here we get the number of block in which we will divide the array
        bloque=0; // here specify the current block
        leng=longitud/k; // here is the number of element in each block
        if(longitud%k===0){ // if we can have the same number of element in each block we continue
            for(j=0;j<peaks.length;j++){ //here we record each  peak
                if(Math.floor(peaks[j]/leng)===bloque){ // if we found one peak in the current block we increase to the next block in order to check it
                    bloque += 1;
                }
            }
            if(bloque===k){ // if there is one element in each block we update the variable current.
                current = k;
            }
        }
        
    }
    return current;
}