Takes an array of stock prices, assuming each entry represents successive daily averages, and determines what optimal buy and sell dates would've been.

stock_picker.rb

# Takes an array of stock prices, assuming each entry
# represents average price on successive days, and
# determines what optimal buy and sell dates would've been.

def stock_picker(stock_prices_array)
    hypothesis = [0,0,1] # [Hypothetical profit, buy time, sell time]
    
    i = 0
    while i < stock_prices_array.length
        if_buy = i
            
        j = i unless stock_prices_array[i+1] == nil
        break if stock_prices_array[i+1] == nil
        
        while j < stock_prices_array.length
            if_sell = j
            
            if stock_prices_array[j] - stock_prices_array[i] > hypothesis[0]
                hypothesis[0] = stock_prices_array[j] - stock_prices_array[i]
                hypothesis[1] = i
                hypothesis[2] = j
            end
        j += 1
        end
    i += 1
    end
    
    return hypothesis
end

# EXAMPLE
puts stock_picker([17,3,6,9,15,8,6,1,10])

# Highest potential profit is 12 units if you buy at cell 1 price and
# sell at cell 4 price