pick_peaks.py

# ~ In this kata, you will write a function that returns the positions and the values of the "peaks" (or local maxima) of a numeric array.

# ~ For example, the array arr = [0, 1, 2, 5, 1, 0] has a peak at position 3 with a value of 5 (since arr[3] equals 5).

# ~ The output will be returned as an object with two properties: pos and peaks. Both of these properties should be arrays. If there is no peak in the given array, then the output should be {pos: [], peaks: []}.

# ~ Example: pickPeaks([3, 2, 3, 6, 4, 1, 2, 3, 2, 1, 2, 3]) should return {pos: [3, 7], peaks: [6, 3]} (or equivalent in other languages)

# ~ All input arrays will be valid integer arrays (although it could still be empty), so you won't need to validate the input.

# ~ The first and last elements of the array will not be considered as peaks (in the context of a mathematical function, we don't know what is after and before and therefore, we don't know if it is a peak or not).

# ~ Also, beware of plateaus !!! [1, 2, 2, 2, 1] has a peak while [1, 2, 2, 2, 3] does not. In case of a plateau-peak, please only return the position and value of the beginning of the plateau. For example: pickPeaks([1, 2, 2, 2, 1]) returns {pos: [1], peaks: [2]} (or equivalent in other languages)

# ~ Have fun!

def pick_peaks(arr):
    
    pos, peaks, aux  = [], [], []
    max = 0

    for i in range(len(arr)):
        if arr[i] > arr[i-1]:
            max = i
            aux.append("u")
        elif arr[i] < arr[i-1]:
            aux.append("d")
        if len(aux) == 3:
            if (aux[0] == "u" and aux[1] == "u" and aux[2] == "d") or (aux[0] == "d" and aux[1] == "u" and aux[2] == "d"):
                pos.append(max)
                peaks.append(arr[max])
                max = i+1
            del aux[0]
    
    output = {"pos": pos, "peaks": peaks}
    
    return output
#pick_peaks