def nge(array):
_nge = [-1 for i in array]
s = Stack()
for i in range(len(array)):
element = array[i]
while not s.is_empty() and element > array[s.peek()]:
_nge[s.peek()] = i
s.pop()
s.push(i)
return _nge
def compute_left_smaller_diffs(array):
s = Stack()
diff_array = [None for i in array]
for i in range(len(array)):
element = array[i]
while not s.is_empty() and s.peek() > element:
s.pop()
if s.is_empty():
diff_array[i] = 0
else:
diff_array[i] = s.peek()
s.push(element)
return diff_array
def calculate_span(stocks):
spans = [-1 for i in stocks]
s = Stack()
s.push(-1)
spans[0] = 1
for i in range(len(stocks)):
# pop until we find a taller element in stack
while s.peek() != -1 and stocks[s.peek()] <= stocks[i]:
s.pop()
# calculate span
spans[i] = i - s.peek()
s.push(i)
return spans
def print_common_nodes(root1, root2):
s1 = Stack()
s2 = Stack()
while True:
# push left nodes of trees to stack
if root1:
s1.push(root1)
root1 = root1.left
elif root2:
s2.push(root2)
root2 = root2.left
elif not s1.is_empty() and not s2.is_empty():
root1 = s1.peek()
root2 = s2.peek()
if root1.data == root2.data:
# found match, check next in both trees
print root1.data,
s1.pop()
s2.pop()
root1 = root1.right
root2 = root2.right
elif root1.data < root2.data:
# move to next node in first tree
s1.pop()
root1 = root1.right
# set this to none or in the next iteration it gets
# pushed to s2 again
root2 = None
else:
s2.pop()
root2 = root2.right
root1 = None
else:
break
def find_largest_area(hist):
s = Stack()
n = len(hist)
max_area = 0
i = 0
while i < n:
# Push as long as stack top is smaller
if s.is_empty() or hist[s.peek()] <= hist[i]:
s.push(i)
i += 1
else:
# pop one by one and calculate area considering, the popped
# elements height as the smallest. notice we are not
# incrementing i here. Hence we keep popping until we find
# a smaller height
s_top = s.pop()
# width is from top to i, but not including i
width = i if s.is_empty() else i - s.peek() - 1
area_with_top_as_smallest = hist[s_top] * width
if max_area < area_with_top_as_smallest:
max_area = area_with_top_as_smallest
# pop entire stack to consider all elements
while not s.is_empty():
s_top = s.pop()
# here i is N, so width will be from top to N, not
# including N
width = i if s.is_empty() else i - s.peek() - 1
area_with_top_as_smallest = hist[s_top] * width
if max_area < area_with_top_as_smallest:
max_area = area_with_top_as_smallest
return max_area
def nge(array):
s = Stack()
for num in array:
while not s.is_empty() and s.peek() < num:
print s.pop(), '-', num
s.push(num)
while not s.is_empty():
print s.pop(), '-', -1
def build_lowest_number_removing_k_digits(num, k):
s = Stack()
l = len(num) - k
for c in num:
if not s.is_empty() and int(s.peek()) > int(c) and k > 0:
s.pop()
k -= 1
s.push(c)
return ''.join(s.get_list()[:l])
def convert(exp):
k = -1
exp = list(exp)
s = Stack()
for i in range(len(exp)):
if is_operand(exp[i]):
k += 1
exp[k] = exp[i]
elif exp[i] == '(':
s.push(exp[i])
elif exp[i] == ')':
while not s.is_empty() and s.peek() != '(':
k += 1
exp[k] = s.pop()
if not s.is_empty() and s.peek() != '(':
return -1
else:
s.pop() # pop off the '('
else:
while not s.is_empty() and precedence(exp[i]) <= precedence(
s.peek()):
k += 1
exp[k] = s.pop()
s.push(exp[i])
while not s.is_empty():
k += 1
exp[k] = s.pop()
return ''.join(exp)[0:k + 1]
def is_pre_order(array):
s = Stack()
root = -maxint
for value in array:
while not s.is_empty() and s.peek() < value:
root = s.pop()
if value < root:
return False
s.push(value)
return True
def get_balanced_stack(string):
s = Stack()
for c in string:
if c == '{' or s.is_empty():
s.push(c)
else:
if s.peek() == '{':
s.pop()
else:
s.push(c)
return s
def dupe_found(string):
s = Stack()
for c in string:
exp = ""
if c != ')':
s.push(c)
else:
while not s.is_empty() and s.peek() != '(':
char = s.pop()
exp += char
if not is_exp(exp):
return True
s.pop()
return False
class Queue2(object):
def __init__(self):
self.stack1 = Stack()
self.stack2 = Stack()
def push(self, element):
self.stack1.push(element)
def pop(self):
if self.stack2.is_empty():
while not self.stack1.is_empty():
self.stack2.push(self.stack1.pop())
return self.stack2.pop()
def peek(self):
if self.stack2.is_empty():
while not self.stack1.is_empty():
self.stack2.push(self.stack1.pop())
return self.stack2.peek()
def find_max_len(string):
n = len(string)
result = 0
s = Stack()
s.push(-1)
for i in range(n):
if string[i] == '(':
s.push(i)
else:
s.pop()
if not s.is_empty():
result = max(result, i - s.peek())
else:
s.push(i)
return result
