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#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright © 2019 Manoel Vilela
#
# @project: Project Euler
# @author: Manoel Vilela
# @email: manoel_vilela@engineer.com
#
"""
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%.
"""
def bouncy(num: int) -> bool:
digits = str(num)
comparisons = set()
for d1, d2 in zip(digits, digits[1:]):
if d1 == d2:
continue
state = 1 if int(d1) > int(d2) else 0
comparisons.add(state)
if len(comparisons) == 2:
return True
return False
def bouncy_counter(threshold: float):
bouncy_numbers = 0
n = 100
percentage = 0
while percentage < threshold:
n += 1
if bouncy(n):
bouncy_numbers += 1
if bouncy_numbers > 0:
percentage = bouncy_numbers / n
return n
def main():
print(bouncy_counter(0.99))
if __name__ == '__main__':
main()