def get_path(graph, from_s, from_t):
"""Traces the searchers to create and return a list of indices
representing the shortest path from s to t. Assumes that the
search is already complete and that a path has been found.
Args:
graph: A Graph instance.
from_s, from_t: Searcher instances.
Returns:
A list of integers.
"""
path = []
# We first construct the path from s to the connection point. Using
# a stack ensures that the order is correct.
start_stack = Stack()
while from_s.backtracer is not None:
start_stack.push(from_s.backtracer)
from_s.backtracer = graph[from_s.backtracer].backpointer
while not start_stack.is_empty():
path.append(start_stack.pop())
# Then we extend the path from the connection point to t.
while from_t.backtracer is not None:
path.append(from_t.backtracer)
from_t.backtracer = graph[from_t.backtracer].backpointer
return path
def pop_at(self, index):
if index > self.piles.size()-1:
raise "Invalid index."
temp_stack = Stack()
for i in range(index, 0, -1):
temp_stack.push(SetOfStacks.pop_stack(self))
item = self.piles.pop()
self._backfill(temp_stack.reverse(), self.piles)
return item.pop()
def f1(n):
"""Prints an English phrase that describes an input integer.
Args:
n: Any int with absolute value less than one nonillion (10^30).
Raises:
ValueError: n has absolute value greater than 10^30.
"""
if n == 0:
print("Zero")
return
neg = True if n < 0 else False
n = abs(n)
output_stack = Stack()
three_stack = Stack()
group = -1
# Divide n into "groups" of three digits: the pre-thousands, then
# thousands, then millions, billions, and so on. For each group,
# generate a string such as "Two Hundred Twelve" and push onto a
# stack s.t. groups with greater significance will be output first.
while n > 0:
for i in range(3):
three_stack.push(n % 10)
n //= 10
hundreds = three_stack.pop()
tens = three_stack.pop()
ones = three_stack.pop()
output_stack.push(three_digit_string(hundreds, tens, ones))
group += 1
print_output(output_stack, neg, group)
def __init__(self): self.queue = Stack()
def _create_new_stack(self):
self.piles.push(Stack())
def __init__(self):
self.piles = Stack()
self._create_new_stack()
