def lvp(s):
stk = Stack()
max_len = 0
curr_len = 0
for c in s:
if c == '(':
stk.push(c)
else: # c == ')'
if stk.pop() is None:
max_len = curr_len if curr_len > max_len else max_len
curr_len = 0
else:
curr_len += 2
return curr_len if curr_len > max_len else max_len
def parChecker(symbolString):
'''
General Balanced Symbol Problem
'''
s = Stack()
index = 0
balanced = True
while index < len(symbolString) and balanced:
symbol = symbolString[index]
if symbol in "[{(":
s.push(symbol)
else:
if s.isEmpty():
balanced = False
else:
top = s.pop()
if not matches(top, symbol):
balanced = False
index = index + 1
if balanced and s.isEmpty():
return True
else:
return False
def postfixEval(postfixExpr):
operandStack = Stack()
tokenList = postfixExpr.split()
for token in tokenList:
if token in "0123456789":
operandStack.push(int(token))
else:
operand2 = operandStack.pop()
operand1 = operandStack.pop()
result = doMath(token, operand1, operand2)
operandStack.push(result)
return operandStack.pop()
def lvp(s):
if s is None:
return 0
stk = Stack()
max_len = 0
curr_len = 0
for c in s:
print "Evaluating char:", c
if c == "(":
stk.push(c)
continue
try:
stk.pop()
curr_len += 2
print "TRY BLOCK: curr_len =", curr_len
except Exception as e:
max_len = max(max_len, curr_len)
curr_len = 0
print "Max Len =", max_len, "Curr Len =", curr_len
print "Finally Max Len =", max_len, "Curr Len =", curr_len
return max(max_len, curr_len)
def removeLongestSubstring(s):
stk = Stack()
#stk.push(-1)
maxLen = 0
currLen = 0
for i in range(len(s)-1, -1, -1):
char = s[i]
if char == '0':
stk.push(char)
if currLen > 0:
currLen = 0
continue
# char == '1'
# pop 2 0's for every 1.
j = 0
while not stk.isEmpty and j < 2:
stk.pop()
j += 1
if j == 2:
currLen += 3
maxLen = max(currLen, maxLen)
return maxLen
def reverseString(self, originalString):
stk = Stack()
for i in originalString:
stk.push(i)
print(stk.items)
while not stk.isEmpty():
print(stk.pop())
def baseConverter(decNumber, base):
'''
Method to convert decimal to any base
'''
digits = "0123456789ABCDEF"
remStack = Stack()
while decNumber > 0:
rem = decNumber % base
remStack.push(rem)
decNumber = decNumber // base
baseString = ""
while not remStack.isEmpty():
baseString = baseString + digits[remStack.pop()]
return baseString
def infixToPrefix(infixexpr):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
infixexpr = infixexpr[::-1]
opStack = Stack()
prefixList = []
tokenList = infixexpr.split()
for token in tokenList:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
prefixList.append(token)
elif token == "(":
opStack.push(token)
elif token == ")":
topToken = opStack.pop()
while topToken != "(":
prefixList.append(token)
topToken = opStack.pop()
def infixToPostfix(infixexpr):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
opstack = Stack()
postfixList = []
tokenList = infixexpr.split()
for token in tokenList:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYYZ" or token in "123457890":
postfixList.append(token)
elif token == "(":
opstack.push(token)
elif token == ")":
topToken = opstack.pop()
while topToken != "(":
postfixList.append(topToken)
topToken = opstack.pop()
else:
while (not opstack.isEmpty()) and (prec[opstack.peek()] >=
prec[token]):
postfixList.append(opstack.pop())
opstack.push(token)
while not opstack.isEmpty():
postfixList.append(opstack.pop())
return " ".join(postfixList)
def reverse_stack(stack):
r_stk = Stack()
while not stack.isEmpty():
r_stk.push(stack.pop())
return r_stk
#!/usr/bin/python
from ds.Stack import Stack
def reverse_stack(stack):
r_stk = Stack()
while not stack.isEmpty():
r_stk.push(stack.pop())
return r_stk
if __name__ == "__main__":
stk = Stack()
stk.push(4)
stk.push(3)
stk.push(2)
stk.push(1)
print stk.items
rev_stk = reverse_stack(stk)
print rev_stk.items