mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-27 23:11:09 +00:00
88b6caa30a
* Create infix_to_prefix_conversion.py * Create postfix_evaluation.py * Update balanced_parentheses.py
62 lines
2.8 KiB
Python
62 lines
2.8 KiB
Python
"""
|
|
Output:
|
|
|
|
Enter an Infix Equation = a + b ^c
|
|
Symbol | Stack | Postfix
|
|
----------------------------
|
|
c | | c
|
|
^ | ^ | c
|
|
b | ^ | cb
|
|
+ | + | cb^
|
|
a | + | cb^a
|
|
| | cb^a+
|
|
|
|
a+b^c (Infix) -> +a^bc (Prefix)
|
|
"""
|
|
|
|
def infix_2_postfix(Infix):
|
|
Stack = []
|
|
Postfix = []
|
|
priority = {'^':3, '*':2, '/':2, '%':2, '+':1, '-':1} # Priority of each operator
|
|
print_width = len(Infix) if(len(Infix)>7) else 7
|
|
|
|
# Print table header for output
|
|
print('Symbol'.center(8), 'Stack'.center(print_width), 'Postfix'.center(print_width), sep = " | ")
|
|
print('-'*(print_width*3+7))
|
|
|
|
for x in Infix:
|
|
if(x.isalpha() or x.isdigit()): Postfix.append(x) # if x is Alphabet / Digit, add it to Postfix
|
|
elif(x == '('): Stack.append(x) # if x is "(" push to Stack
|
|
elif(x == ')'): # if x is ")" pop stack until "(" is encountered
|
|
while(Stack[-1] != '('):
|
|
Postfix.append( Stack.pop() ) #Pop stack & add the content to Postfix
|
|
Stack.pop()
|
|
else:
|
|
if(len(Stack)==0): Stack.append(x) #If stack is empty, push x to stack
|
|
else:
|
|
while( len(Stack) > 0 and priority[x] <= priority[Stack[-1]]): # while priority of x is not greater than priority of element in the stack
|
|
Postfix.append( Stack.pop() ) # pop stack & add to Postfix
|
|
Stack.append(x) # push x to stack
|
|
|
|
print(x.center(8), (''.join(Stack)).ljust(print_width), (''.join(Postfix)).ljust(print_width), sep = " | ") # Output in tabular format
|
|
|
|
while(len(Stack) > 0): # while stack is not empty
|
|
Postfix.append( Stack.pop() ) # pop stack & add to Postfix
|
|
print(' '.center(8), (''.join(Stack)).ljust(print_width), (''.join(Postfix)).ljust(print_width), sep = " | ") # Output in tabular format
|
|
|
|
return "".join(Postfix) # return Postfix as str
|
|
|
|
def infix_2_prefix(Infix):
|
|
Infix = list(Infix[::-1]) # reverse the infix equation
|
|
|
|
for i in range(len(Infix)):
|
|
if(Infix[i] == '('): Infix[i] = ')' # change "(" to ")"
|
|
elif(Infix[i] == ')'): Infix[i] = '(' # change ")" to "("
|
|
|
|
return (infix_2_postfix("".join(Infix)))[::-1] # call infix_2_postfix on Infix, return reverse of Postfix
|
|
|
|
if __name__ == "__main__":
|
|
Infix = input("\nEnter an Infix Equation = ") #Input an Infix equation
|
|
Infix = "".join(Infix.split()) #Remove spaces from the input
|
|
print("\n\t", Infix, "(Infix) -> ", infix_2_prefix(Infix), "(Prefix)")
|