Project Euler 112 - Bouncy numbers

'''
Working from left-to-right if no digit is exceeded by the digit to its left it is called an increasing number; for example, 134468.
Similarly if no digit is exceeded by the digit to its right it is called a decreasing number; for example, 66420.
We shall call a positive integer that is neither increasing nor decreasing a "bouncy" number; for example, 155349.
Clearly there cannot be any bouncy numbers below one-hundred, but just over half of the numbers below one-thousand (525) are bouncy.
In fact, the least number for which the proportion of bouncy numbers first reaches 50% is 538.
Surprisingly, bouncy numbers become more and more common and by the time we reach 21780 the proportion of bouncy numbers is equal to 90%.
Find the least number for which the proportion of bouncy numbers is exactly 99%.
'''

# FUNCTION 1
def isIncreasing(n):
    s = str(n)
    counter = 0
    length = len(s)
    for i in range(length-1):
        if int(s[i]) <= int(s[i+1]):
            counter += 1
    if counter == length-1:
        return True
    else:
        return False


# FUNCTION 2
def isDecreasing(n):
    s = str(n)
    counter = 0
    length = len(s)
    for i in range(length - 1):
        if int(s[i]) >= int(s[i + 1]):
            counter += 1
    if counter == length - 1:
        return True
    else:
        return False


# FUNCTION 3
def isBouncy(n):
    if isDecreasing(n) == False and isIncreasing(n) == False:
        return True
    return False


# FUNCTION 4
def bouncyProportion(proportion):
    n = 1
    counter = 0
    counter += isBouncy(1)
    prop = counter / n
    while prop != proportion:
        n += 1
        counter += isBouncy(n)
        prop = counter / n
    return n


# MAIN FUNCTION
print(bouncyProportion(0.5))
print(bouncyProportion(0.9))
print(bouncyProportion(0.99))