stock_span.py

# Context : The span Si of the stock’s price on a given day i
# is defined as the maximum number of consecutive days just before
# the given day, for which the price of the stock on the current
# day is less than or equal to its price on the given day.

# Problem: We have a series of n daily price quotes for a stock
# and we need to calculate span of stock’s price for all n days


def calculate_span(stock_quotes, span):
    # span for the first quote will always be 1
    span[0] = 1
    for i in range(1, len(stock_quotes), 1):
        # initialize span value to be 1 for each ith quote
        span[i] = 1
        # scan for all the quotes to the left
        j = i - 1
        # if the preceeding quote has a value less than or equal to current quote
        # increase the span value of the current quote
        while j >= 0 and stock_quotes[i] >= stock_quotes[j]:
            span[i] = span[i] + 1
            j = j - 1
    return span


quotes = [10, 4, 5, 90, 120, 80]
# initialize span as an empty list with same length as quotes
span_list = [None] * len(quotes)
print(calculate_span(quotes, span_list))
# Result : [1, 1, 2, 4, 5, 1]