Is there a way to add parentheses to a math expression which is stored in a string? [closed]

Question

I'm trying to figure out a way to add parentheses to a math expression. I don't have any idea how to start with the pseudo code for this issue. Do I need to begin with If statements or is there another way to do this in Java or Kotlin? So basically I want the string to transform.

From this:

val before = "10-2*3/4"

To this:

val after = "((10-2)*3)/4"

Answer 1

Split the string in chunks, that are alternatively numbers and operators. Assuming that there are n operators, start with n-1 left parenthesis, write first number, first operator, second number, then repeatedly write a right parenthesis, operator, number until you exhaust the string.

E.g. with 10 - 2 * 3 / 4, we have n=3 and output

((
  10-2
      )*3
         )/4

Answer 2

You can turn your math expression into postfix and then using a stack, add parentheses to it. Here is a Python code snippet demonstrating this:

#infix to postfix
def to_postfix(infix):
s=Stack()
postfix=""
operand_sort={'/':2,
'*':2,
'+':1,
'-':1,}
for token in infix:
    if token in '0123456789':
        postfix+=(token)        
    else:
        postfix+=(" ")        
        while (not s.is_empty()) and (operand_sort[s.top()] >= operand_sort[token]):
            postfix+=(s.pop())
            postfix+=(" ")        
        s.push(token)
while not s.is_empty():
    opToken=s.pop()
    postfix+=(" ")        
    postfix+=(opToken)

return postfix

def setparantheses(postfix):

s=Stack()
items = postfix.split()
for token in items:
    if token.isnumeric():
        s.push(token)        
    else:
        exp1 = s.pop()
        exp2 = s.pop()
        s.push("("+exp2+token+exp1+")")
return s.pop()

Sorry I didn't give you Java or pseudocode but you get the idea.